IMPROVED_PREAMP

Published:2009/7/6 2:04:00 Author:May | From:SeekIC

Replaces inefficient input circuit of inexpensive frequency counter, to ensure accurate counting from DC to over 60 MHz Circuit brings input signal waveform to TEL level of 3.5 V P-P while providing required perfect square waves down to lowest-frequency input signal. Input circuit is balanced FET source-follower having extremely high input impedance. Back-to-back diodes provide overload protection. Input stage drives 733 differential video amplifier having 100-MHz band-width and gain of 400. 2N709 switching transistor squares preamp signal for TTL translator using two sections of 74H00 high-speed quad NAND gate. Circuit requires dualpolarity sup ply delivering at least 63 mA; regulation is optionaL-G. Beltrami, High-Impedance Preamp and Pulse Shaper for Frequency Counters, Ham Radio, Feb. 1978, p 47-49.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Amplifier_Circuit/IMPROVED_PREAMP.html

Print this Page | Comments | Reading(3)