Low voltage adjustable signal amplifier?

smp375

Joined Mar 21, 2009
14
I would like to build a circuit that can amplify by 0-50%, a variable low voltage (0.0-1.0VDC) signal, but I need to have an adjustable output. Where do I start?

t_n_k

Joined Mar 6, 2009
5,455
Hi smp375,

Not clear about your specification - but if you never need to amplify by more than 100% then you actually have an attenuator. At its simplest this could be done with a potentiometer between the source and output.

Maybe you have a more detailed statement of your requirement.

smp375

Joined Mar 21, 2009
14
Well, my electronics experience is extremely limited, with only a basic understanding of most components and their functions, basic principles of electricity, soldering, and schematic reading.
The best way I can describe my requirement is that I have a variable DC signal that can be anywhere between 0 and 1 volt. I would like to take control of that voltage by being able to step it up between 0 to .5 volts. So the input would be between 0 to 1 volt, output would be .5 to 1.5 volts at max gain, but still needs to be able to vary between 0 to 1 volt at minimum gain. Is that better? Then, if it's not too difficult, (this isn't as important) I would like the maximum output not to be able to exceed 1 volt, even at maximum gain. I understand that last part may be more difficult to achieve.

t_n_k

Joined Mar 6, 2009
5,455
Still unclear about from where the input is derived - is it a DC supply for instance...?

and what is the output being fed to ...?

In principle you need a level shifter.

You could try something like the attached circuit ...

View attachment Level shiter.pdf

VR1 (200Ω pot) is adjusted to set the 0.5V output offset. The LM134 is temperature sensitive so the offset will drift over a large temperature range - can be allowed for

See the LM134 data sheet http://www.national.com/mpf/LM/LM134.html

The LM134 will operate over a reasonably wide input voltage range so the 9V is just a suggestion - if you want to use a battery say - which could run down in voltage a few volts without compromising operation.

Note: The circuit may not integrate well with your input/output requirements.

I'm sure there are plenty of other options - I was looking at something reasonably easy to make and test.