Simple Voltage Follower with Input Compensation


This is a simple form circuit for implementation the function of the LM12 IC. This circuit is shown the LM12 is prone to low-amplitude oscillation bursts coming out of saturation if the high-frequency loop gain is near unity. This is the figure of the circuit.

The R2C2 combination across the input works with R1 to reduce feedback at high frequencies without greatly affecting response below 100 kHz. A lead capacitor, C1, improves phase margin at the unity-gain crossover frequency. Proper operation requires that the output impedance of the circuitry driving the follower be well under 1 kX at frequencies up to a few hundred kilohertz.

Simple Transient Voltage Circuit


This is a design circuit transient voltage that is built by LM340. This is a simplest form design. The figure of the circuit is shown in below.

If transients exceed the maximum rated input voltage of the device, or reach more than 0.8V below ground and have sufficient energy, they will damage the regulator. The solution is to use a large input capacitor, a series input breakdown diode, a choke, a transient suppressor or a combination of these. [Circuit source: National Semiconductor Notes].

Simple Remote Sensor


This circuit is shown a simple design for sensing the remote. This circuit allows the op amp to correct for dc drops in cables connecting the load. This is the figure of the circuit.

This circuit is work with based on LM12 IC. The cable drop will affect transient response. Degradation can be minimized by using twisted, heavy-gauge wires on the output line. Normally, common and one input are connected together at the sending end. [Schematic’s circuit source: National Semiconductor Notes].

Simple Regulator Floating Ground


This is a design for simplest form circuit the regulator. This circuit is control by LM340. This is the figure of the circuit.

When the ground pin alone becomes disconnected, the output approaches the unregulated input, causing possible damage to other circuits connected to VOUT. If ground is reconnected with power “ON”, damage may also occur to the regulator. This fault is most likely to occur when plugging in regulators or modules with on card regulators into powered up sockets. Power should be turned off first, thermal limit ceases operating, or ground should be connected first if power must be left on.

Simple Parallel Operation for Power Amplifier


Output drive beyond the capability of one power amplifier can be provided as shown here. This circuit is work with based on LM12 IC. This is the figure of the circuit.

The power op amps are wired as followers and connected in parallel with the outputs coupled through equalization resistors. A standard, high-voltage op amp is used to provide voltage gain. Overall feedback compensates for the voltage dropped across the equalization resistors. With parallel operation, there may be an increase in unloaded supply current related to the offset voltage across the equalization resistors. More output buffers, with individual equalization resistors, may be added to meet even higher drive requirements.

Simple 80W Operational Amplifier Using LM12


This is a circuit for op amp that is built by LM12. This circuit can deliver 80W of sine wave power into a 4X load with 0.01% distortion. This is the figure of the circuit.

The IC delivers g10A output current at any output voltage yet is completely protected against overloads, including shorts to the supplies. The dynamic safe-area protection is provided by instantaneous peak-temperature limiting within the power transistor array. The turn-on characteristics are controlled by keeping the output open-circuited until the total supply voltage reaches 14V. [Circuit’s source: National Semiconductor Notes].

Simple DC to DC Converter Circuit


This is a circuit for converter voltage. This circuit is DC to DC converter using a standard 12 VAC center tapped power transformer wired as a blocking oscillator. The circuit is not very efficient but will produce a high voltage usable for low power applications. This is the figure of the circuit.

The input battery voltage is raised by a factor of 10 across the transformer and further raised by a voltage triple consisting of three capacitors and diodes connected to the high voltage side of the transformer. The circuit draws about 40 milliamps and should operate for about 200 hours on a couple of 'D' alkaline batteries. Higher voltages can be obtained by reducing the 4.7K bias resistor.

Simple 12V to 120V Inverter Circuit


This is a simple design for inverter that produces 12V to 120V voltage and frequency line. This circuit is work with based on the transistor. The wattage depends on which transistors you use for Q1 and Q2, as well as how "big" a transformer you use for T1. The inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts. This is the figure of the circuit.

The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger of the microwave is the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The gauge of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. That is all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each. Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1, Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power. The capacitor is using tantalum.

C1, C2 - 68 uf, 25 V Tantalum Capacitor
R1, R2 - 10 Ohm, 5 Watt Resistor
R3, R4 - 180 Ohm, 1 Watt Resistor
D1, D2 - HEP 154 Silicon Diode
Q1, Q2 - 2N3055 NPN Transistor (see "Notes")
T1 - 24V, Center Tapped Transformer (see "Notes")

Simple Single Op Amp Band Pass Filter


This is a circuit design for a band pass filter. A band pass filter passes a range of frequencies while rejecting frequencies outside the upper and lower limits of the pass band. The range of frequencies to be passed is called the pass band and extends from a point below the center frequency to a point above the center frequency where the output voltage falls about 70% of the output voltage at the center frequency. This is the figure of the circuit.

The filter bandwidth (BW) is the difference between the upper and lower pass band frequencies. The quality factors, or Q of the filter is a measure of the distance between the upper and lower frequency points and is defined as (Center Frequency / BW) so that as the pass band gets narrower around the same center frequency, the Q factor becomes higher. For a single op-amp band pass filter with both capacitors the same value, the Q factor must be greater than the square root of half the gain, so that a gain of 98 would require a Q factor of 7 or more.

Simple Multiple Pulse Generator Circuit


This is a circuit for generate the pulse of timer circuit. This circuit is used to ring my doorbell rapidly three times when a car pulled into my driveway. This circuit is based on 555 timer IC. This is the figure of the circuit.

R2 and C2 set the output frequency. Use a diode and resistor to change the duty cycle, if desired. R1 and C1 set the cycle time which sets the number of pulses. R3 can be deleted if you have other loads on the power supply. The circuit is activated by applying power to it. The first pulse will be longer than the others.

Simple Inverter for Florescent Lamps


This circuit is very easy to construct, reliable, and even powerful enough to light up a 15W florescent tube. This circuit is constructs from transistor NPN and some components. This is the figure of the circuit.

This is a single transistor oscillator circuit. Current passed through primary winding inducts a magnetic field to the core and the core gives the energy back to the feedback winding with a delay determined by the core material and windings. System then oscillates continuously on a frequency depending on this timing. You cannot use 2SD882 with voltages over 4.5 volts. It is only needed if you are going to feed the circuit with only 4.5 volts.

Simple 555 Pulse Generator


This is another circuit for generate the pulse of timer circuit. The first positive pulse from a classic 555-based oscillator is always 1.6 times longer than the following pulses. The difference is caused by the fact that only during the first cycle C2 starts charging up from 0 V. This is generally not a problem, but sometimes this first pulse just should be the same length as the rest - at least approximately. This is the figure of the circuit.

The picture shows the oscillator and an addition to it (everything to the right from the Vs-Gnd axis) that can solve the problem. Immediately after switch-on, C2 is empty and the voltage on the gate of Q2 is low. Q2 is off and it makes C2 charge up very quickly through Q1 and R3 until it reaches just below Vs/3. Then Q2 turns on, Q1 turns off, and the classic circuit continues to charge and discharge C2 relatively slowly between 2Vs/3 and Vs/3. As the voltage on C2 never again drops below Vs/3, Q2 now conducts all the time and Q1 is permanently off.

Active Band Pass Filter


Active band pass filters are simply filters constructed by using operational amplifiers as active devices configured to simulate inductors or what are known as "gyrators". Active band pass filters are used largely at audio frequencies where otherwise the size of the inductor would become prohibitive.

The are many different types of active filters including high pass, low pass, band reject and there are numerous responses including multiple feedback band pass (MFBP), dual-amplifier band pass (DABP) and, state variable bi-quad all pole circuits. Interestingly all known filter responses such as Butterworth and Chebyshev may be synthesised.

Simple Line Driver Circuit


This is a design circuit for stereo line driver for feeding long cables or buffering an audio source. This is a simple circuit design. This circuit is a pre amp. This is the figure of the circuit.

This preamplifier has low output impedance, and is designed to drive long cables, allowing you to listen to a remote music source without having to buy expensive screened cables. The very low output impedance of around 16 ohms at 1KHz, makes it possible to use ordinary bell wire, loudspeaker or alarm cable for connection. The preamplifier must be placed near the remote music source, for example a CD player. The cable is then run to a remote location where you want to listen. The output of this preamp has a gain of slightly less than one, so an external amplifier must be used to drive loudspeakers.

Simple 22 Watt Audio Amplifier Circuit


This is a design for simple audio power amplifier. This circuit is based on amplifier chip TDA1554 that is has two channel audio chip amp. This is the figure of the circuit.

The circuit can be used as a booster in a car audio system, an amp for satellite speakers in a surround sound or home theater system, or as an amp for computer speakers. The circuit is quite compact and uses only about 60 watts. The circuit works best with 4 ohm speakers, but 8 ohm units will do. The circuit operates at 12 Volts at about 5 Amps at full volume. Lower volumes use less current, and therefore produce less heat.

R1 39K 1/4 Watt Resistor
C1,C2 10uf 25V Electrolytic Capacitor
C3 100uf 25V Electrolytic Capacitor
C4 47uf 25V Electrolytic Capacitor
C5 0.1uf 25V Ceramic Capacitor
C6 2200uf 25V Electrolytic Capacitor
U1 TDA1554 Two Channel Audio Amp Chip
MISC Heat sink for U1, Binding Posts (For Output), RCA Jacks (For Input), Wire, Board

Simple Voltage Regulator using Op Amp


This circuit is a circuit diagram power supply. Circuit diagram works on voltage +13.8 V 5A with electric currents. This circuit controlled by the LM338 IC. This is the figure of the circuit.

Many times we need a supply of relatively strong in the framework we provide a variety of equipment with + 13.8V, as transceivers CB, cargo lead-acid batteries, and others known to use the circuit capable of providing complete in his exit, when This continuously operating 5A and 12A peak current. Not only need a few external components. Setting the voltage at + 13.8V to the trimmer TR1, (multiturn). The IC1 LM338 must in each case is placed on one suitable heat sink, which both supported by one fan. All the connections by the circuit become with big cross-section cable, because the current through from within their already high enough.

R1=270R 1/4W 2%
TR1=4k7 (Multiturn)
C1=10000uF 40V
C2-3=100 nF 100V Polyester
C4-5=10uF 25V
D1-2=1N4002 (1A/100V)
B1=25A Bridge Rectifier
T1=220Vac/15VAC – 8A Mains Transformer
S1=2 Pole Single Throw Mains Switch
F1=250mA Fuse

Simple Pierce XTAL Oscillator Circuit Using JFET


This circuit is conventional “Pierce” type oscillator that uses a JFET. The circuit uses fundamental mode crystals. It has decent performance and reliability if we use a low noise JFET. This is the figure of the circuit.

The feedback is controlled by the C1 Capacitance from drain to ground. Adjusting the frequency can be done by adjusting a shunt capacitance C2 across the crystal. The crystal works in parallel mode. This circuit is suitable where some crystals should be switched in and out to select the frequency, as there’s no tuning required.

Simple LED Current Sense Circuit


This is a design circuit for the physical implementation of the LED current sense circuitry assuming the thermal fold back circuitry is a simple current source. This circuit is based on the LM3424 uses an external current sense resistor (RSNS) placed in series with the LED load to convert the LED current (ILED) into a voltage (VSNS). This is the figure of the circuit.

The HSP and HSN pins are the inputs to the high-side sense amplifier which are forced to be equal potential (VHSP=VHSN) through negative feedback. For matching and noise performance, the suggested signal current ICSH is approximately 100 μA. This current does not flow in the LEDs and will not affect either the off-state LED current or the regulated LED current. ICSH can be above or below this value, but the high-side amplifier offset characteristics may be affected slightly. [Circuit’s Source: National Semiconductor, Inc]

Simple HF Bands QRP Linear Amplifier


This is the design for QRP linear amplifier with a wide frequency response; within three dB's from 300KHz to 30MHz. Overall gain is in the region of 16dB and the final output power may be well over four watts. This is the figure of the circuit.

The wide bandwidth is a result of the construction of the RF transformers, T1 and T2. These are wound on 2-hole ferrite balun cores as commonly found in the old fashioned valve TV sets (e.g. Phillips 4322-020-31520). Twist 2 lengths of 22 SWG enamelled wire together and wind as shown. Connect the end of the "A" winding to the start of the "B" winding. Use this junction as the centre-tap of the transformer. This PA will deliver 4 watts continuously (with a suitable heatsink), and may be loaded into a short-circuit or open circuit without causing damage. This makes it almost the ideal PA for outdoor/field use. Above is the full circuit diagram of the RFPA and the coil winding pattern. This PA may be used for for SSB, as well as CW (and AM?).

Simple FET Audio Mixer Circuit


This is a simple project circuit for mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consume very little power. This is the figure of the circuit.

This circuit is based on or built by FET 2N3819. The circuit can be powered by a single 9 volt battery. As many or as few channels as are required can be added to the mixer. A shielded case is probably needed to reduce hum and help stop oscillations.

R1, R3 10K Pot
R2, R4 100K 1/4 W Resistor
R5 6.8K 1/4 W Resistor
C1, C2, C3 0.1uF Capacitor
Q1 2N3819 Junction FET
MISC Wire, Shielded (Metal) Case, Phone or Other Plug For Output

Simple Automatic Nicad Battery Charger Circuit


Many cheap battery chargers usually assume that charging the battery slowly is OK although the battery is already full of charges. All they do is usually charging the battery with constant current no matter if the battery is almost completely discharged or has been fully charged. Off course the battery wouldn’t be damaged immediately after few charging cycles, but actually they’re damaged slowly and the life time can’t be maximized. This is one of solution for the problem above.

This circuit is automated that you don’t have to manually set the alarm timer to wake you up when your battery has been fully charged so you can unplug the charger to prevent overcharging. This battery sense the voltage while charging the battery, and automatically stop the charging when it’s fully charged. This is the figure of the circuit.

To set the R8, turn the variable resistor R8 to its maximum value (highest resistance), connect a fully charged Nicad battery (about 1.44V) to the batteryn terminal. Press and release the start push button, and make sure the LED D1 is turned on after releasing the start push button. Now turn the R8 slowly toward its minimum value and stop turning exactly when the LED D1 turned off. Now your automatic Nicad battery charger is ready. Place a discharged battery and press the start button, the D1 LED will turn on to indicate that the charging is in progress. LED D1 will turn off after the battery has been fully charged. To provide multiple battery charging, make few more similar circuits shown in the dashed line box, and you can charge up to ten Nicad battery (50 mA charging current per battery) using 1 Ampere 9-12 volts transformer.

Simple Audio Power Amplifier Over Temperature Detector


This is a power amplifier for audio that has over temperature detector inside. This circuit is based on LM56 as controller. This circuit has simple form of the design. This is the figure of the circuit.

An audio power amplifier IC is bolted to a heat sink and an LM56 Celsius temperature sensor is mounted on a PC board that is bolted to the heat sink near the power amplifier. To ensure that the sensing element is at the same temperature as the heat sink, the sensor's leads are mounted to pads that have feed through to the back side of the PC board. Since the LM56 is sensing the temperature of the actual PC board the back side of the PC board also has large ground plane to help conduct the heat to the device. The comparator's output goes low if the heat sink temperature rises above a threshold set by R1, R2, and the voltage reference. This fault detection output from the comparator now can be used to turn on a cooling fan. The circuit as shown in design to turn the fan on when heat sink temperature exceeds about 80°C, and to turn the fan off when the heat sink temperature falls below approximately 75°C. [Circuit source: National Semiconductor, Inc Notes].

Simple Transistor Tester Circuit Device


This non transistor tester circuit devices that isn’t accurate, but utility of this test device enough assisting in assaying of quality of transistor. This circuit can show promise about condition of a transistor is still in condition either or have been in condition of breakdown. Besides, earns also applied to test amplification of current from the transistor is categorizing transistor type A (amplifier of current 140 - 270), transistor type B (270 - 500), or transistor type C (amplification > 500).

This very simple circuit work principle. Transistor tested receives bases current around 10mA through R1. With assumption that transistor is still be good, the thing will yield strain at R2 until R4 and depend on position of switches S2, some of this voltage compared to to a reference voltage by utilizing IC 1. Mode of action from circuit which its inside is also approximately equal, only inside of circuit destined for PNP transistor. The supply of the voltage is required by this circuit only from battery.

Wein - Bridge Oscillator Using TLV2471


The Wien - Bridge oscillator is one of the simplest and best known oscillators and is used extensively in circuits for audio applications. The figure in the below shows the basic Wien bridge circuit configuration. On the positive side, this circuit has only a few components and good frequency stability. The major drawback of the circuit is that the output amplitude is at the rails, which saturates the op-amp output transistors and causes high output distortion. This is the figure of the circuit.

The Wien – Bridge oscillator circuit is shown in the figure, with component values selected to provide an oscillation frequency of ù0 = 2ðf0, where f0 = 1/(2ðRC) = 1.59 kHz. The circuit oscillated at 1.57 kHz, caused by varying component values with 2.8% distortion. This high value results from the extensive clipping of the output signal at both supply rails, producing several large odd and even harmonics. The feedback resistor was then adjusted ±1%. Figure 9 shows the output voltage waveforms. The distortion grew as the saturation increased with increasing RF, and oscillations ceased when RF was decreased by a mere 0.8%.

Touch Switch Circuit Using Logic Control


This is a touch circuit that is used as a latching circuit to switch a LED ON and OFF by physically touching the ON metal plate or OFF metal plate. This circuit is based on logic gate for control the operation. This is the figure of the circuit.

It is important to ensure that 9V battery is used as its DC source. If one uses the mains supply to step down the voltage using a transformer for rectification and filtering to get the 9V DC supply, ensure that the transformer is designed in such a way that it follows the safety standard requirement of UL. This is important to ensure the safety of the user that is using the metal contacts to ON/OFF the LED. [Schematic diagram source: Electronics Project Design].

Simple Remote Doorbell Warning Switch Circuit


This circuit should only be used with the solenoid type chime doorbells, the electronic type that play tunes will not work here. This is the simple circuit design.

The basic principle work is the hardest part for this circuit was the title. It is quite easy to miss the sound of a doorbell if you are watching the television, this circuit gets round the problem by providing a visual indication, i.e. a lamp. As an alternative, a LED could also be used. You could just parallel a lamp across the doorbell, but this would mean extra drain from the doorbell batteries or transformer. Using a series resistor R1 actually reduces current flow, and if run from batteries, will give them a longer life. The value of R1 is chosen so that about 0.6 to 0.7 volts is dropped across it, and the doorbell should still ring. I used a combination of a 22 ohm resistor in parallel with a 50 ohm. The doorbell still rang and circuit operated correctly. I used to have an electromechanical counter that registered each time when someone pressed the switch.

Simple Car Battery Charger Circuit


This is a circuit for battery charger. But the circuit can places in a car. This is a simple design and useful to make it. In this circuit there is facility for monitoring the charging current and voltage. This is the figure of the car battery charger.

The circuit is based on the IC MC78T12ABT. The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps the mains voltage to 15V AC and diodes D1&D2 does the job of rectification. The transformer T1 can be a 230V primary; 15-0-15V, 3A secondary step down transformer. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3, D4 and D5. So the output from the IC1 will be a regulated 14.1V (12+2.1).The battery is charged via diode D6.The D6 blocks reverse flow of current from battery to charging circuit when the mains power is not available.

Simple Amplifier Using LM386


This is the low frequency power amplifier of which the penumbra article can be composed without using it is hardly. The about 660-mW output can be gotten with the 16-ohm speaker.

This circuit is used for the simple monitor and so on. The impedance (4-ohm and 8-ohm, and so on), the output power of the speaker and so on are specified by the standard but are OK rather than strict. Because the sound cracks (warping) when presenting the output above the rating, it uses naturally within the standard. When conscious of the timbre and the output power, it is better not to do the use of this circuit.

LCD Thermometer Circuit with LM35


The LM35 of National Semiconductors that is used in this project is a precision centigrade temperature sensor, which has an analog output voltage. It has a range of -55ºC to +150ºC and an accuracy of ±0.5º C. The output voltage is 10mV/ºC. The output voltage is converted by the AD convertor of the AT Mega8. The temperature is displayed on an LCD module. This is the figure of the circuit.

In this example the thermometer has a range of 0ºC to 40ºC and a resolution of 0.5ºC. If you want to have a read out in Fahrenheit you can use the LM34. The software for this project is written in BASCOM AVR. The BASCOM AVR compiler has build in commands for reading out the ADC port of a AVR microcontroller. The result is displayed on a LCD module in a discrete value of the temperature and in a bar-graph. The AT Mega8 has a A/D converter which can give an output of 210 = 1024 discrete values. When a 5V supply is used you have a resolution of 5000mV/1024 = 4.8mV. Because the LM35 has a output of 10mV/C the resolution of the thermometer is 10mV/4.8mV ~ 0.5ºC. The LCD module has 20 columns. In the scale of 0ºC to 40ºC every column represents 2ºC. [Circuit’s Source: National Semiconductor, Inc].

Integrator Circuit


Integrator op-amp this circuit also comes from inverting circuit with the feedback prisoner is changed with capacitor. This is the figure of the Integrator Circuit.

Usually circuit for application there are addition of parallel prisoner with capacitor with name of RF. Integrator circuit which has not in adding parallel prisoner with capacitor. ROM Value is between zero up to R1.

Simple 8 Watt Flouroscent Lamp Driver


This is a design circuit of a simple flouroscent lamp driver circuit based on two transistors. The circuit uses capacitive ballasting for driving the tube. An 8 Watt standard flouroscent tube can be efficiently driven using the circuit.

The two transistors (2SC1983) with associated components form an oscillator around 1KHz. The oscillator is wired so that saturation conditions of the transistors are prohibited. This adds on to the efficiency of the circuit. The circuit produces a clean sine wave with very less noise. The winding details (no of turns) are given in the circuit. Use 0, 8 mm diameter enameled copper wire for primary and 0, 4 mm diameter enameled copper wire for secondary. The primary should be wound first and secondary on top of it. The circuit is use a 12 V battery or 12 V DC power supply as the DC voltage source.

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