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
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
Attachments
Jocko,
why must that output coupling cap be so huge? 100µ? Does the circuit only work with 2k5 output load? 😕
why must that output coupling cap be so huge? 100µ? Does the circuit only work with 2k5 output load? 😕
NICE! Thanks Jocko. Looks like I have something to play with over the weekend.
Hey, I must have missed that you had boards for this. I though your DAC boards didn't include IV conv, right?
mlloyd1
Hey, I must have missed that you had boards for this. I though your DAC boards didn't include IV conv, right?
mlloyd1
1.) Why so big?
I picked the part closest to me on the work bench.
2.) Other values work too. I use around 4K.
3.) I had some old I/V boards laying around since '89. Some one asked if I had anything to go with the DAC board, and the next thing you know, they were all gone.
New ones......eventually.
Jocko
I picked the part closest to me on the work bench.
2.) Other values work too. I use around 4K.
3.) I had some old I/V boards laying around since '89. Some one asked if I had anything to go with the DAC board, and the next thing you know, they were all gone.
New ones......eventually.
Jocko
IV Converter
Hi Jocko,
Nice to see you back. I thought you had left us.
I see a common base amplifier between to current sources or should I say between current source and current sink?
My problem is I don't like common base amplifiers....
All the best.😉
Hi Jocko,
Nice to see you back. I thought you had left us.
I see a common base amplifier between to current sources or should I say between current source and current sink?
My problem is I don't like common base amplifiers....
All the best.😉
If you carefully adjust the current, it will work.
Yes, it is a common-base. Not an RF engineer, eh? I am, so I do.
Jocko
Yes, it is a common-base. Not an RF engineer, eh? I am, so I do.
Jocko
Jocko, why do you need the current source Q4? Isn't this circuit like on-off, to much gain to be useful? Feedback???
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.....
Art
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.....
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
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
I know that because of the VAS line the BJT's will compensate them selfs out regarding the output voltage but is it that much?!
But i have not measured it.... I can understand you have ... respect!!
But i have not measured it.... I can understand you have ... respect!!
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