Hi,
You think you could post a schematic rather than have us search through a bunch of posts to see what you actually want to do? I think this would help a lot for people reading this thread. I know it would help me to understand you better.
+/-33V outputs - What opamp could I use?
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11th February 2012 10:53 AM #1atferrari
+/-33V outputs - What opamp could I use?
I wonder if is it possible to do something similar to what is proposed here
PWM Signal to LM317 to adjust Voltage Output
but this time to get two control signals: one from 0 to +33V to control an LM317 and another from 0 to -33V to control an LM337.
I imagine two separate opamps, one powered between 0 and +38V and the other between -38V and 0V. (I have those +/-38V DC available from an old power supply).
What could be the most suitable opamps?
Searching through Farnell I can at least compare some but the prices of the suitable(?) ones is scary. To come to my hands I have to think of them multiplied around 4 times!!
Maybe I am overlooking something...
Any suggestions? GraciasAgustín Tomás
In theory, there is no difference between theory and practice. In practice, however, there is.
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11th February 2012 12:40 PM #2MrAl
0One test is worth a thousand expert opinions, but one expert specification is worth a thousand tests.
If i miss something you posted or something you think is important, feel free to PM me.
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11th February 2012 12:59 PM #3alec_t
If I understand you correctly you want one PWM signal to give two simultaneous outputs; one of them negative (0 to -33) and the other positive (0 to 33) ?
0My circuit designs should be regarded as experimental. Although they work in simulation, their component values may need altering or additional components may occasionally be necessary when the circuit is built. Due safety precautions should be taken with any circuit involving mains voltage or electrostatic-sensitive components.
Alec's First Law:-
Every problem has a solution (given the right information and resources).
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11th February 2012 03:03 PM Thread Starter #4atferrari
Here it is
I believed it was better to read about the idea until reaching the circuit. But OK, that is me.
Here it is
PWM Signal to LM317 to adjust Voltage Output
Two independent PWM signals; each one controlling one regulator. That is why I think of having them powered between common and its respective rail (single supply).
My concern is the type (and COST) of the opamps I could use.0Agustín Tomás
In theory, there is no difference between theory and practice. In practice, however, there is.
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11th February 2012 03:22 PM #5alec_t
The op-amps themselves aren't critical as they don't have to withstand 33V. You could run them at, say, 12V and use them to drive BJTs or FETs switching loads operating from 33V.
0Last edited by alec_t; 11th February 2012 at 03:24 PM.
My circuit designs should be regarded as experimental. Although they work in simulation, their component values may need altering or additional components may occasionally be necessary when the circuit is built. Due safety precautions should be taken with any circuit involving mains voltage or electrostatic-sensitive components.
Alec's First Law:-
Every problem has a solution (given the right information and resources).
-
11th February 2012 05:02 PM #6ronsimpson
High voltage op amps are not so common but:
AD8274
ADA4004
LTC6104, LTC6103, LT1013
AD5749
OP4177
PA340CC
PA341CE0
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12th February 2012 08:50 PM #7alec_t
Perhaps this? Almost any opamp (I used a LM324 model) with rail to rail input will do. Not having a LM317 or LM337 model I used LT1085 and LT3015 respectively. There are two 0V to +5V PWM inputs (from a micro). One opamp has a 5V supply, the other a -5V supply. The regulators have +33V and -33V supplies respectively.
0My circuit designs should be regarded as experimental. Although they work in simulation, their component values may need altering or additional components may occasionally be necessary when the circuit is built. Due safety precautions should be taken with any circuit involving mains voltage or electrostatic-sensitive components.
Alec's First Law:-
Every problem has a solution (given the right information and resources).
-
14th February 2012 11:13 PM Thread Starter #8atferrari
Will try it.
Busy with vessels right now but I will try it.
Gracias.0Agustín Tomás
In theory, there is no difference between theory and practice. In practice, however, there is.
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