This is a circuit that is performance requirements necessitate analog output current monitors to swing within 100mV of zero. This is the figure of the circuit.
A1, a chopper stabilized amplifier, has a clock output. This output switches Q1, providing drive to the diode-capacitor charge pump. The charge pump output feeds A1’s V– terminal, pulling it below zero, permitting output swing to (and below) ground. If desired, negative output excursion can be limited by either clamp option shown. Reliable start-up of this bootstrapped power supply scheme is a valid concern, warranting investigation. In Figure D2, the amplifier’s V– pin (Trace C) initially rises at supply turn-on (Trace A) but heads negative when amplifier clocking (Trace B) commences at about midscreen.
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