gain amplifiers 3

[jecca]

Is it possible to design an amplifier with a gain < 1? If yes, how would I go about it? All the gain amps I find have a gain of 1 or higher.

 

[nbucska]

I assume you are talking about op.amp. circuit.
Let assume a gain of 1/3
The wiring of basic DIFFERENTIAL amplifier:
input + --- R1.1 ( .1 AND .2 ARE THE ENDS OF R1)
R1.2 --- IN+ ---R2.1
R2.2--- GND
input- ---R3.1
R3.2 --- IN- --- R4.1
R4.2 --- OP.OUT
-------VALUES : --------------
R1= 3 * R2
R3=R1
R3 = 3 * R4
------------------------
INVERTING AMP:
omit R1 AND short R2.
IN+ --- GND
-----------------------
NON-INVERTING AMP:
omit R3 AND R4
R1= 2 * R2
IN- --- GND

 

[lkm]

If a device has a gain less than 1, we may call it attenuator. In low power and fix attenuation value, we use something like a resistors network to form it.

In the case, we need a high power or using in an Auto Gain Control circuit, sometime we need a variable attenuator. This type of attenuator we always use the active component to build it. It use the same technique as the amplifier to build it.

Expecially in RF circuit, we can find a lot of attenuators with FET inside.

 

[jbartos]

Suggestion: Consider DC amplifiers. Then, one that has a resistor Rf in feedback and R in the input. The voltage amplification will be
Vout=-(Rf/R)Vin
If Rf<R the amplifier will be producing output voltage smaller than the input voltage.

 

[jecca]

Thank you sooo much to nbucska, lkm, jbartos. Your replies were very helpful.

 

[Trex77]

A voltage divider (adj pot at bottom end) feeding an opamp follower works well.