28_VAC_CURRENT_LIMITER

Published:2009/7/13 5:00:00 Author:May | From:SeekIC

Dual JFETs in voltage-sharing arrangement protect output of 28-VAC power amplifier. Transistors should be matched for IDSS. During positive half-cycle of input, Q2 operates as current Iimiter and Q1 as source follower. If Q1 does not supply enough current, drain voltage of Q2 drops and makes Q1 turn on further. Conversely, if Q1 supplies too much current, Q2 drain voltage rises and tends to turn Q1 off. On negative half-cycle, Q1 becomes limiter and Q2 is source follower. -J. P. Thompson, Current Limiter Protects Amplifier from Load Faults, EDN Magazine, June 5, 1978, p 148 and 150.



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