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# Can you step down voltage using Op Amp?

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#### Reborn718

##### Newbie level 5
Hi everyone,
Today I go over the Operational Amplifier notes, suddenly there is something coming up to mind. Since the Operational Amplifier can amplifier the input voltage, we can reduce the input signal by making the gain less than 1. Can we used the operational amplifier for step up or step down the AC voltage? From what I know, operational amplifier is a linear system. I doubt that wen can't step up or step down the AC voltage using Op Amp...I need you guys ideas about this...=D

You've kinda lost me,

But yes, if Rf is smaller than Rin then the gain will be below unity and the output will be proportionally smaller than the input. Is that what you're asking?

I would like to know if I can use Op Amp as the transformer to step up or step down voltage...

Transformer, depending on the wining ratio, can step-up or step-down voltages following the power(energy) preservation concept, that is:
U[input]*I[input]*efficiency => U[output]*I[output] ***
In other words, you can convert low-current, high-voltage input to high-current, low-voltage, high-current, low-voltage to low-current, high-voltage and so on ..

An Opamp can be used to reduce voltage or to amplify voltage (formula *** doesn’t apply), but the output is limited by the supply rails of the Opamp; if you use so called ‘rail-to-rail’ opamp you can expect the output voltage swing close to the rail-to-rail voltage, but not higher !!!
And don’t forget about the fact that opamps require external power supply, transformers don’t ..

Regards,
IanP

Reborn718 said:
Hi everyone,
Today I go over the Operational Amplifier notes, suddenly there is something coming up to mind. Since the Operational Amplifier can amplifier the input voltage, we can reduce the input signal by making the gain less than 1. Can we used the operational amplifier for step up or step down the AC voltage? From what I know, operational amplifier is a linear system. I doubt that wen can't step up or step down the AC voltage using Op Amp...I need you guys ideas about this...=D

If you want a gain of less than one just use a resistor.

Hi !!!
If you want a gain <1 you have to use the opamp in the inverting configuration :
Vout=-G.Vin
If you want a gain >1 you connectt your input at the non inverting input of the opamp and then
Vout=(1+G).Vin

But don't forget that opamp are designed to work on signals, you shouldn't use them to create a power rail.
The output current of the opamp are usualy limited to +/-15mA, and they are linear devices. All the power that you don't use is dissipated in the opamp.
Bye

GAIN IS THE RATIO OF FEEDBACK REG AND SERIES REG. SELECT FREEBACK REG LESSER AS SERIES. ATTENUATION CAN BE ACHIEVD.

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