Multiplying Voltage by a factor

[Prakash Gautam]

I am trying to make a data aquisition system that converts analog voltage to digital value by use of ADC. Since the voltage input range of ADC is limited (5V in the device I am using), but my aquisition system needs to record voltages more than this. So I would want to attenuate higher voltage and magnify the smaller voltages. So how I am thinking of op amp for the purpose. So how can I make one?

Any references are welcome.
Thank you in advance.

 

[Arouse1973]

Trans diode Logarithmic amplifier might work. This scales down large input signals and allows you to measure them while still allowing small signal to be measured. But the output is the log of the input so you will need to convert it back in software if you need to.

Adam

 

[KrisBlueNZ]

Sounds like you want some kind of auto-ranging system like multimeters have. This requires a variable attenuator that selects between several attenuation factors (often with 10:1 ratios) under software control.

You need to tell us a lot more about your application and requirements.

 

[OLIVE2222]

You can also use an ADC with a variable or selectable voltage reference, again under software control.

 

[Prakash Gautam]

Sounds like you want some kind of auto-ranging system like multimeters have. This requires a variable attenuator that selects between several attenuation factors (often with 10:1 ratios) under software control.

You need to tell us a lot more about your application and requirements.

My input voltage range is 0-20V and I want to pass this voltage through some circuit so that I get the output 0-5v ( $V_0=.25*V_i$)

 

[(*steve*)]

Is there any reason you can't use a resistive voltage divider?

Are you just passing the voltage, or does the circuit you're passing it to expect to sink some current from it (if so, how much)?