In this paper we investigate how to use controlled
circuit instability in the filtering and amplification of narrow
pulses. The basic circuit consists of a first-order RC network
coupled to a negative resistance controlled by an external
quench generator, which yields alternating periods of stability
and instability. The study shows that when the circuit acts as a
signal generator it can produce narrow exponential or
Gaussian pulses, depending on the quench waveform applied.
Included as a receiver front end, the circuit behaves as a highgain
narrow-pulse filter. We also estimate the circuit
parameters required to generate and receive sub-nanosecond
pulses.