... is it the Early effect that affects the performance of the second schematic ? I mean that since the transistor help the reference current transistor to provide a little current to the base of Q1, I suppose that the current on base would be very close on the Q1 and Q2 and therefore the collector current too, but I surprised by the result of the simulation, it doesn't seem to improve at all ! Do you think it's early effect that affect the performance of the second
The main effect of additional "degeneration" emitter resistances is feedback, among others increasing the output resistance and thus reducing the Early effect.I also tried with resistors placed on the emitters to reduce the VCE voltage.
The ambiguity of the term noise may be a problem here. If you're operating near sensor noise limits, transistor noise will be most likely a serious problem, and a strong point against basic current mirrors as bias sources. Degenerated current mirrors can perform better, simple load resistors operated with sufficient voltage are probably superior.This permit to provide a better noise immunity from the supply rails, I don't know if it's relevant for noise which come from the transistors added for this architecture.
For your above shown schematic I'd suggest to use the center tap of your R5 (use two 1.5k resistors in series).Pspice ask me a source for the noise analysis, how can I do ...?
Pspice ask me a source for the noise analysis, how can I do ...?
In this case, what does the voltage source represent ? is it just to have a voltage reference to deduce the noise contribution of the stage ? what is the voltage value could you suggest me ?In this, case, I would place an equivalent circuit (a resistor with a series voltage source) for the photoconductive sensor
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