# Voltage Amplifier?

Discussion in 'General Electronics' started by dmt1, Jun 3, 2004.

1. ### dmt1Guest

Hi

Just wondering if there is any device that would allow me to amplify a
voltage by 1 log unit (ie. a factor of 10). I have something that is
outputing at approx 0.045VDC but the sensor will only detect if it is
in the order of 0.45VDC. I don't know the reason for the descrepancy
but i was just wondering if there is anything i can do to amplify the
output signal?

Thanks

2. ### Robert BaerGuest

A good linear solution is to use an operational amplifier, with the
gain set to 10.
You can have a gain of either +10 or of -10 as you wish.
Op amp ICs are cheap as heck, resistors toset the gain are also very
cheap.
The power supply could be as meager as a single 9V battery, or a 10 to
30V wall wart, or a special +15V / -15V supply.

4. ### Robert StankowicGuest

Depends on the type of signal and the required precision. Your
question lets me guess that it is low frequency and the precision is
not critical, in this case any cheap OpAmp will do:

|\
-IN to +INPUT ----| \_________________OUT
----|1K|----| / |
| | |/ |
| | |
GND | |
----|10K|-----
use a trimpot here

Most of them work with supply voltages from +/-3 to +/- 18 VDC
For higher precision/frequency get the datasheet of the OpAmp, many of
them have circuit examples.

5. ### Ben MossGuest

Actually that should be a 9K ohm, not a 10K (when you use the positive
input the gain is 1 + R2/R1). A trimpot is still a good idea,
considering tolerances of typical resistors.

|\
-IN to +INPUT ----| \_________________OUT
----|1K|----| / |
| | |/ |
| | |
GND | |
----|9K|------
use a trimpot here

HTH,
-Ben

6. ### Robert StankowicGuest

Of course. Thank you for pointing that out.

7. ### JeffMGuest

that should be a 9K ohm
or you could specify values that are actually available
(no matter the tolerance).
http://www.token.com.tw/resistor/resistor-color-code.htm

|\
-IN to +INPUT ----| \_________________OUT
---- 2K ----| / |
| | |/ |
| | |
GND ---- 18K ------