Instrumentation amplifier and Crystal Microphones
Instrumentation amplifier and Crystal Microphones
(OP)
I am trying to amplify the singals from two crystal microphones. I need the signals to be matched as exactly as possible. My employer purchaced the LT1101 and I am unable to get that to work, and I cannot find good application notes. Are there any other chips/amplifiers etc that will work more effectively with an Xtal mike?
Thanks
Thanks





RE: Instrumentation amplifier and Crystal Microphones
RE: Instrumentation amplifier and Crystal Microphones
RE: Instrumentation amplifier and Crystal Microphones
If you insist on using it, instead of an electret, what is your supply voltage to the LT1101? How do you have it wired? Do you have bias resistors on the inputs to the amp?
Why would you use an instrumentation amp? They are very noisy.
RE: Instrumentation amplifier and Crystal Microphones
RE: Instrumentation amplifier and Crystal Microphones
Any Opamp needs some source of bias current on the input pins. In your case, that could be a resistor to ground. Without looking at the datasheet, I can't give you a correct value for the resistor, but try a 1megohm for starts. Put a 1meg resistor between each amp input pin and ground. If that doesn't bring the output up, try a 100Kohm instead.
How are you connecting the output of the inst. amp.? What are you using to determine the output signal level? Are you overloading the amp output? Check the datasheet for available output current. Some inst. amps are quite weak.
A 9V battery is a fine power source, but you are running a single ended supply, and the inst. amp is trying to swing about ground. Connect another 9V battery, such that the negative terminal goes to the V- pin on the amp, the one you currently have grounded, and the positive terminal of the battery goes to ground. This will allow the output signal of the amp to swing about ground.