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Signal Maximizing or Minimizing Circuit

IP.com Disclosure Number: IPCOM000052007D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

West, DL: AUTHOR

Abstract

This very simple circuit allows easy detection of whether an external adjustment is improving or reducing the amplitude of a high frequency AC signal (IN). If the adjustment begins to reduce the signal amplitude, the LED (light-emitting diode) immediately shuts off, while increasing amplitude keeps the LED turned ON.

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Signal Maximizing or Minimizing Circuit

This very simple circuit allows easy detection of whether an external adjustment is improving or reducing the amplitude of a high frequency AC signal (IN). If the adjustment begins to reduce the signal amplitude, the LED (light- emitting diode) immediately shuts off, while increasing amplitude keeps the LED turned ON.

The values of R1, R2, C1 and C2 determine the frequency range of the AC signals which could be handled. The R1, C1 and R2, C2 time constants should be such that on both inputs of the comparator (COMP) the signals go to peak value and stay close to it as long as the envelop of the IN signal remains constant. When the envelop increases, the fast time constant circuit (R2, C2) follows the envelop variation faster than the other circuit (R1, C1), but the relative polarity at the comparator input remains unvarying and the LED remains ON. When the envelop goes down, the signal on the faster time constant circuit goes down faster, which reverses the relative polarity on the comparator inputs and switches the LED off.

By reversing the comparator inputs 3 and 4, a minimum (null) AC adjustment circuit is provided.

To insure a controlled discharge rate on capacitors C1 and C2, resistors should be connected across them. The discharge time is otherwise controlled by the input resistance of the comparator circuit which may vary from one device to another.

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