Help me with designing a particular amplifier circuit

amplifier circuit

Hello,
I have only two 1.5V batteries (as VCC & -VCC for an Opamp).
I want to amplify a signal whose maximum absolute voltage is 1.5V.
I want the output voltage peak be amplified to 2.5V.
can you design a circuit to do so?
thanks.

amplifier circuit

well, you can, it depends your opamp's structure.

Re: amplifier circuit

LM741 Opamp for example.
the only restriction is that we have two 1.5V batteries only.

Re: amplifier circuit

You must use an Opamp that is rail-to-rail to make amplification go to the alimentation as possible.
It can be 2 ways to configurate the amplifier.
One is using the battery in center taped to give +1.5V and -1.5V the simpliest.

The other is using the 3V 1.5 +1.5 and use the configuration above.

The 1/2 tension must be provided with resistor with high values for not discharge the battery
The calculations for the acupuling capacitor is simple and varies with the minimal frequecy that you want to work in this case is 20hz.

C1 with R1//R2 makes an high pass filter. c1 acupled the signal
C2 with charge makes an high pass filter too desacupeled the output.
R4 and C3 makes and low pass filter and C3 block the dc to be amplified.
R1 and R2 creates the the rect of charge. 1/2 of Vcc
The grafical shows the input signal and output
Both circuit are non inverting.
The gain is given by Av = 1+ R3/R4
C3 decrease a litile the gain and must be calculated C = 1/(2*Π*R*F)
Now is just an question to adjust the values as you want
Regards

Re: amplifier circuit

but in both of them, VCC restriction have been forgotten. the peak to peak output voltage should be 5V (= 2.5V - (-2.5V)). but output peak to peak of these opamps can not exceed 3V (= VCC - VEE).

Re: amplifier circuit

The first step is to build a dc-dc converter that will boost voltage from 3V to 5V, or more .. an example of 3-to-5 is attached ..
Then you can use an opamp and generate the required output ..

Regards,
IanP

Re: amplifier circuit

Hi
Your maximum output swing thoritically is (Vcc+) - (Vcc-) which is 1.5+1.5=3 Volt
Of cource you can't even reach this swing practically.

Your specs are not correct. Kinly try to correct it

Thanks
Haytham

Re: amplifier circuit

IanP: Well, but very expensive and low efficiency.

I think We should connect in series some fraction of the input signal and output voltage of opamp. isn't it possible?

Re: amplifier circuit

Hi Alitavakol,

If you have got a small 1:1 transformer on hand, you could combine this with
a low-voltage rail-to-rail opamp and include it in the feedback loop. Maybe
you could wind one yourself. Don't shoot me, at least I've got the resistor
values right.

on1aag.