Precision Peak Value Detector

The circuit

While rectifiers have to convert ac power into dc power with the highest possible efficiency, a detector should demodulate radio frequency carriers with the best possible linearity. In the earlier times, radio engineers were concerned with sensitivity because quality amplifiers were still unavailable. Crystals were used as the detecting element to sense the weak electromagnetic fields. Today's semiconductor diodes have their origin in these early crystal detectors. Rectification efficiency improves by increasing the bend of the diode characteristic. Low voltages occur with small curvatures.

The input file

precision peak value detector

.control
tran 2ms 1s 0 0.5ms
plot v(1)/2+2 v(3)/10 v(4)-2 xlabel t[s] ylabel 'v(1) v(3) v(4) [V]'
  + title 'TRAN analysis'
.endc

v1 5 1 dc 0 sin 0 1V 10Hz 0.1s
v2 5 0 dc 0 sin 0 1V 10Hz 0.4s

r1 1 2 100k
r2 2 4 100k

c1 4 0 10uF

e1_amp 3 0 0 2 1meg

d1 3 4 noname
d2 2 3 noname

.model noname d (bv=10V rs=30k)

.end

The results