I have a circuit which I have designed to pull down a voltage via sinking current into the opamp output. When the source signal is of higher output impedance this works fine, but when the source signal impedance is lower the minimum voltage which this signal can be pulled down to is affected by the opamp output impedance. This source signal is supplied at max 20mA.
In the circuit the opamp will pull the input voltage (VF3) down via the diode to the voltage set on VG2, but can not push the voltage above the input voltage due the diode being reversed biased.
Does someone maybe have a suggestion as to how this could be improved via adding a transistor on the opamp output? E.g have the transistor base connected to the opamp output and the collector connected to the diode negative? I hope to be able to pull this voltage down to a much lower value, ideally rail to rail.
Thanks in advance!