high input range amplifier

[shahinjc]

hi guys
i wanna build a volt meter from range 500 micro volt to 5 volt
i need a front end amplifier or op amp which support this range as its input
any suggestion?:-o

 

[betwixt]

PGA202 possibly. It has digitally programmable gain in steps of 1, 10, 100 and 1,000.

Brian.

 

[shahinjc]

PGA202 possibly. It has digitally programmable gain in steps of 1, 10, 100 and 1,000.

Brian.

thanks
but i need that the input voltage of this amplifier from range 500 micro volt to 5 volt and in PGA202 data sheets i didn't see its input range , are there anything else ?
a good op amp or somthing?

 

[jiripolivka]

The bottom limit is defined by noise. If you measure a DC voltage, check the opamp 1/f noise and use a low-pass filter to limit noise bandwidth. You also have to define the input impedance to refer the noise power and voltage. The higher the imedance, the higher the noise level.
If you refer to audio frequency range, then there are many mV meters with that range, even down to a fraction of a microvolt.

 

[shahinjc]

The bottom limit is defined by noise. If you measure a DC voltage, check the opamp 1/f noise and use a low-pass filter to limit noise bandwidth. You also have to define the input impedance to refer the noise power and voltage. The higher the imedance, the higher the noise level.
If you refer to audio frequency range, then there are many mV meters with that range, even down to a fraction of a microvolt.

thanks this is really helpful
yes my frequency is low and it's between 40 to 50 hz , so what op amp do you suggest? , i myself found AD620 ,and i think if i set the VS to 6.5 v then my input can be in the range of 500 micro to 5 volt , am i right ?

and what cheap 12 bit ADC do you suggest for this ?

 

[jiripolivka]

I think AD620 is a good choice for your application. I do not work with ADCs but for signals < 100 Hz,AD has some *** ADCs with a refresh of 100 Hz or more. You can try a low-cost DVM which can directly read from ~1 mV AC upwards and with the added AD620 amplifier from microvolts. Some DVMs have an USB link to PC and come calibrated.

 

[shahinjc]

I think AD620 is a good choice for your application. I do not work with ADCs but for signals < 100 Hz,AD has some *** ADCs with a refresh of 100 Hz or more. You can try a low-cost DVM which can directly read from ~1 mV AC upwards and with the added AD620 amplifier from microvolts. Some DVMs have an USB link to PC and come calibrated.

thanks i'm gonna stick to ADC cause i need to process the information with a micro controller