Looking over the design of the stable, temperature compensated CCS, it occurred to me later that introducing a voltage into the third current programming resistor should result in reprogramming the output current, as well as the reference current. I tested this on the iCircuit simulation, and it works! The voltage introduced is differential relative to the Vcc power supply line though, so the curent-control action is sense-inverted. 0.0V in results in maximum current, and the current will decrease as the control voltage is increased. The maximum input control voltage limit is set by the compliance available from the reference current dropping a voltage across the two main current programming resistors near Vcc, plus the transitstor Vbe voltages.
The simulation proved though that the action is quite linear. Below is the simulation circuit, where the second DC voltage source was manually changed in 0.25V increments from 0.00V ≤︎ CV ≤︎ 10.0V, and the output current measured. A GNUPLOT of the collected data follows the simulation circuit.
The simulation proved though that the action is quite linear. Below is the simulation circuit, where the second DC voltage source was manually changed in 0.25V increments from 0.00V ≤︎ CV ≤︎ 10.0V, and the output current measured. A GNUPLOT of the collected data follows the simulation circuit.
Simulation Circuit
Current vs. Voltage Plot
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