Easy-to-build I/V stage

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A variation to the one Jocko supplied:

You'll need a higher +V rail, but won't have the problem of very carefully matching current source and sink.

Any thoughts ?
 

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Marco,

I suppose you mean a dac like the TDA1541 which sinks 0~4mA ?
You need to adjust the current source 2mA higher than the current sink, change R1 to something like 1.5K for 2Vrms output.
Also check that 100u capacitor, since with lower R1 there will be more low frequency roll-off.


you need an dc blocking cap on your output(-)... then it should work to.
Sonnya, this is incorrect. I use the +V rail as common without problems, it's all relative 🙂

Rudolf
 
It would be much better to omit current source Q4, because of the d.c. instability; then replace it with 6k resistor (assuming 1.5 mA collector current of Q2.
For the distortion reduction Q2 can be replaced by complementary feedback (SziKlai) pair
 
Hi Jocko and all others,

I just got this idea. It is the I/V stage for my latest DAC project...(4th allready.. I'm going to be a real DIY pro one day 😉 )

Sorry Jocko, I didn't measure it.. ain't got no distortion or spectrum analyser, but how do you guys feel about this one? I simulates great....but that's just simulation right?


Greetings,
Thijs
 

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Hi Jocko,

I don't understand. Your version has an even higher impedance connected to the colector, being a constant current source. Maybe I should use a CCS too, but wouldn't that increase the gain far too much.....

questions.. questions.... :bawling:

gr,
T
 
Oh brother!............(where art thou.....)

A CCS is supposed to be an infinitely high impedance.

Yes, the gain would higher, except that there is a load resistor hanging off of the CCS to set the gain. That method allows for much lower distortion.

Plus, it adds some PSRR to the circuit, as there is no loop feedback.

Jocko
 
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