A Buffered Precision Peak Detector

** Circuit Description **

* op-amp subcircuit

.subckt uA741         1 2 3 4 5
* connections:        | | | | |
*                     | | | | |
*   non-inverting input | | | |
*         inverting input | | |
*     positive power supply | |
*       negative power supply |
*                        output
*
*
  c1   11 12 8.661E-12
  c2    6  7 30.00E-12
  dc    5 53 dx
  de   54  5 dx
  dlp  90 91 dx
  dln  92 90 dx
  dp    4  3 dx
  egnd 99  0 poly(2) (3,0) (4,0) 0 .5 .5
  fb    7 99 poly(5) vb vc ve vlp vln 0 10.61E6 -10E6 10E6 10E6 -10E6
  ga    6  0 11 12 188.5E-6
  gcm   0  6 10 99 5.961E-9
  iee  10  4 dc 15.16E-6
  hlim 90  0 vlim 1K
  q1   11  2 13 qx
  q2   12  1 14 qx
  r2    6  9 100.0E3
  rc1   3 11 5.305E3
  rc2   3 12 5.305E3
  re1  13 10 1.836E3
  re2  14 10 1.836E3
  ree  10 99 13.19E6
  ro1   8  5 50
  ro2   7 99 100
  rp    3  4 18.16E3
  vb    9  0 dc 0
  vc    3 53 dc 1
  ve   54  4 dc 1
  vlim  7  8 dc 0
  vlp  91  0 dc 40
  vln   0 92 dc 40
.model dx D(Is=800.0E-18 Rs=1)
.model qx NPN(Is=800.0E-18 Bf=93.75)
.ends uA741


** Main Circuit **
* power supplies
Vcc 6 0 DC +15V
Vee 7 0 DC -15V
* input signal source
Vi 1 0 DC 0V PWL ( 0s,-15V 1ms,-7.5V 2ms,-15V 3ms,-15V 4ms,0V 5ms,-15V
+             6ms,-15V 7ms,+7.5V 8ms,-15V 9ms,-15V 10ms,+10V 11ms,-15V )
* limiter circuit 
Xopamp1 1 2 6 7 3 uA741
Xopamp2 4 5 6 7 5 uA741
D1 3 4 D1N4148
D2 2 3 D1N4148
R 2 5 1k
C 4 0 1uF
* model statements
.model D1N4148 D (Is=0.1p Rs=16 CJO=2p Tt=12n Bv=100 Ibv=0.1p)
** Analysis Requests **
.OPTIONS itl5=0
.TRAN 0.5ms 11ms 0s 0.5ms
** Output Requests **
.PLOT TRAN V(1) V(3)
.probe
.end