AVR-Chat

Doug Locke wrote:
>   -----Original Message-----
>   From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com]On Behalf
> Of Russell Shaw
>   Sent: 16 August 2006 01:52
>   To: AVR-Chat@yahoogroups.com
>   Subject: Re: [AVR-Chat] General purpose amplifier to use with AVR
> 
> 
>   Doug Locke wrote:
>   > I wonder if someone could help me with some advice please. I am trying
>   > to use an AVR microcontroller to monitor an analogue signal. The
>   > signal is both very low and of high impedance, so initially I wish to
>   > experiment a little by using a general purpose amplifier between the
>   > source and the AVR. I have found a HP 465A or a Brookdeal 9452 for not
>   > too much cash. Does anyone have any experience with either instrument,
>   > the HP has fixed gains of 20db or 40db while the Brookdeal is
>   > apparently variable 30-100db so either has suitable gain.
>   > Thanks for your time.
>   > Doug Locke.
> 
>   An important thing to specify is the signal bandwidth, or what the source
>   of the signal is. If you're "monitoring" the signal with a digital input,
>   you just need a comparator and simple RC filter. For an ADC input, an
> opamp
>   amplifier and some RFI filtering will do.
 >
 > Thanks Russell
 > Anything with a bandwidth up to say a Mhz would be fine for this. I was
 > rather thinking along the lines of obtaining something general where I had
 > no need to worry about design for now and that would also be an asset for
 > future work. Once I have established the feasability and best approach is
 > the time to look at a specific input circuit.

Hi,
1MHz is quite high for software actions to cope with, other than interrupt-
driven pulse counting. For the ADC, i'd suggest using 1MHz GBW opamps to make
x10 amps with 100kHz BW, or x100 amps with 10kHz BW.