I need to build an input attenuator for my Lynx 2 sound card. like a 10 meg switched input for a VTVM. Mostly to put the voltage I measure in the proper range and to protect it from excessive voltage surges from mistakes.
My idea so far is a string of 10, 1M resistors followed by a unity gain buffer and some 1N4148 diodes to clamp the voltage output to 2 diode drops P-P.
So my problem is this. I need a buffer with low distortion it also must be quiet and have the ability to drive the Lynx 2 single ended.
Also it must have a very high input impedance so it doesn't load the divider string.
BUF03 is obsolete so is BUF04 and a TL071 has issues with a 600 ohm load.
I really only need bandwidth to 100k. Any ideas?
My idea so far is a string of 10, 1M resistors followed by a unity gain buffer and some 1N4148 diodes to clamp the voltage output to 2 diode drops P-P.
So my problem is this. I need a buffer with low distortion it also must be quiet and have the ability to drive the Lynx 2 single ended.
Also it must have a very high input impedance so it doesn't load the divider string.
BUF03 is obsolete so is BUF04 and a TL071 has issues with a 600 ohm load.
I really only need bandwidth to 100k. Any ideas?
a couple of fundamental problems with MegaOhm series resistors
Thermal noise will be large
bandwidth will be restricted with even pF parasitic C
what is your signal range, worst case over voltage to protect against?
Thermal noise will be large
bandwidth will be restricted with even pF parasitic C
what is your signal range, worst case over voltage to protect against?
I need to measure from about 1 or 2 volts up to about 35 v rms from 20Hz to more than 20kHZ with THD down to less than -75 to -80dB.
I'd use something like an OPA827 for the buffer or OPA627
For a divider, check out divider arrays in a DIP. Higher precision.
For a divider, check out divider arrays in a DIP. Higher precision.
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