H&H show a clever current source circuit and challenge readers to prove the circuit works especially without using two of the constraints.
It is a circuit of an opamp driving a bipolar transistor. The base current of the bipolar transistor would normally cause an error. Here the error is compensated. The base current is sensed with the base resistor kR1; the emitter voltage is Vin with the differential voltage added using a circuit configuration resembling a difference amplifier.
The derivation makes no use of the constraints on the resistors. The base current compensation is strictly accurate (assuming ideal opamp).
No comments:
Post a Comment