919A microphone preamplifier

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Circuit board manufacturing pallet with 20 amplifiers shown on 1/4 inch grid graph paper.

If you need to adapt a non-electret audio communications transducer to an electret input, and if you need gain and equalization as well, and if you have limitied space, then the 919A amplifier might be the answer.

The 919A is designed to appear electrically at its output terminals as an electret microphone. It will operate properly when connected to almost any electret microphone input. It is targeted for two-way radio applications where the radio audio input is designed for for an electret microphone, but where it is desired to use a non-electret transducer.

It accomodates a variety of input configurations including electret or dynamic microphones, or any low-level audio signal source. The ground or 'low' terminal of the input can he hard-wired to output ground or floated as a quasi-balanced input in cases where dc is permitted on the input transducer 'low' connection. These configurations have different behavior with different transducers in the presence of high EMI from nearby antennas. Field experiments frequently are the only way to choose the optimal one.

This is a communications product designed for the speech band. The performance limits are based upon the IC used and the physical size of the parts. The 919A has been used in configurations of 100Hz to 10KHz (- 3dB) at 6dB gain, to that of a 1200Hz broad peak with 26dB gain. The nominal current drain is 350 uA.

Please email to Dick Campbell and describe your application.

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