Easy-to-build I/V stage

I have had several requests for my I/V board. SInce they are now all gone, here is something you guys can throw together to hold you over until I build some new ones. It is close (distortion is -70 dB vs. -80 dB; input Z is 5 ohms vs. 0.1 ohms).

Hey, you really didn't think I was going to give you the good one for free did you? [joke]

You may need to tweak the current slightly of either CCS to get the collector of Q2 to a decent voltage. And also R4 to get the emitter of Q2 at exactly 0.0 V. (You guys need something left to try by yourselves.....I'm not going to do it all for you.) [joke]

Jocko
 

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Collector voltage

I would put the 2.49K(R1) resistor on the other side of the 100uf cap(C1)and adjust R3 to get 9 volts or so across R1. You will have real difficulty getting a stable DC votage at the junction of the collectors of Q2 and Q4 without some resistive load to ground at that node. Now please don't beat me up Jocko.....:fight:


Art
 
The reason is the distortion is much worse. I measured it.

The voltage doesn't have to be that stable.......just stable enough to set a decent operating point.

There are more complex variations, but you guys are going to have to figure them out for yourselves. This is just a starting point to prove you don't need op-amps to make a decent I/V stage.

Jocko