OpAmp with variable Voltage

[quaycom]

Hey
I need some help for my project.

I need to have a square wave and a triangle voltage...
I like to use the "standart opamp circuit" im sure u guys know what circuit i mean...

So now my problem... The supply voltage is variable from 20-60Vdc and the peak of the output signals should be arround the same value as the supply voltage...

May one of u guys can help me find a solution....

Thanks


PS: Sorry for my poor english... Im not native in english...

 

[cowboybob]

First thought is a voltage regulator.

You need to tell us a little more, like, why is the supply voltage so variable?

 

[quaycom]

Its a funcion generator, used in systems with system voltage of 24v 48v or 60v (telecom system)
The peak of the output signal should be as near as possible to the system voltage.
So the function generator is powered by the system voltage.
And now i have a signal of 0-5V and I like to amplifie this to 0-(20-60).

Maybe a VGA (variable gain amplifier) is the solution... what u think

 

[unclejed613]

telecom systems use current, not voltage to convey signals. you need a voltage controlled current source, most likely an op amp driving a optoisolator and transistor current source. most op amps can only operate up to 30-36V total rail voltage. beyond that they become "pop-amps"....

in a telecom system, the baseline current is 20mA, and the audio modulates the current +/- 10mA or so.

 

[cowboybob]

This as a fairly simple, generic V-controlled Current amp. Its output could be easily converted to voltage by the addition of a resistive load.

View attachment 61277

Still unsure what your project is, but this may help you to get started.

Keep in mind that it's not necessary for the VCA to handle the voltage levels you cited. Just use this circuit to control another device tasked and designed for the higher potentials.

 

[alec_t]

Here's an amp suggestion for getting the 0-5V function generator output up to at least 100V (the suggested transistors have a 150V rating). Q1 is the gain stage. R4, R5, R6 set the gain to suit 60, 48, 24V supply voltages but could be replaced by a single 1k variable resistor to cope with other voltages. Q2 is an emitter-follower buffer stage. The frequency response of the Q1 and Q2 stages has -3dB points at ~ 15Hz and 1MHz. Q3 and Q4 are a long-tail pair which adjusts the bias of Q1 such that Q1 collector voltage sits at ~ half the supply voltage (set by trimmer R8).

 

[bountyhunter]

I used MOSFETs driven from a couple of logic gates to make a 30V square wave output for my scope calibrator. Could easily be cranked up to higher voltage.

 

[unclejed613]

here's a primer on 20mA current loop telecom transmitters and receivers
**broken link removed**

that one is about digital signalling. apparently for analog signals, anywhere between 20-100mA is a "pass" on telco test sets.