Problem with PSpice Simulation

[zero]

I'm having trouble with a PSpice simulation for a relaxation oscillator
posted in a previous message on sci.electronics.basics: "PUT Oscillator?"

Terry Pinnell was able to model the oscillator succesfully, using the
following netlist:

*Spice netlist for Circuit:
D:\Docs\Electronics\CIRCUITS\C­M\PUT-Diode.CKT
D1 V1_1 C1_1 D1N914
V1 V1_1 0 DC 6V
Q1 Q2_2 Q1_2 V1_1 Q2N2907
Q2 C1_1 Q2_2 0 Q2N2222
C1 C1_1 C1_2 20nF
R2 0 Q1_2 2.2meg
R1 C1_2 Q1_2 22k
.SAVE C1_1 C1_2 V1_1 Q2_2 Q1_2 @d1[p] @d1[id] @v1[p] v1#branch @q1[p]
@q1[ic]
.SAVE @q1[ib] @q1[ie] @q2[p] @q2[ic] @q2[ib] @q2[ie] @c1[p] @c1
@r2[p] @r2
.SAVE @r1[p] @r1

* Selected Circuit Analyses :
.OP
.TRAN 1u 50m 0 1u

* Models/Subcircuits Used:

*1N914 100V 80mA Si Switching Diode pkgIODE0.4 A,K
.MODEL D1N914 D(IS=7.075E-9 RS=0.78 N=1.95 TT=7.2E-9 CJO=4E-12
VJ=0.657
+ M=0.4 BV=100 IBV=0.0001 )

This simulation works correctly for CircuitMaker (using
Spice3f5/XSpice). A picture of the results is at
http://www.terrypin.dial.pipex­.com/Images/Relaxation1.gif




I tried the following netlist in PSpice Lite Version 9.2:

Oscillator
D1 V1_1 C1_1 D1N914
V1 V1_1 0 DC 6V
Q1 Q2_2 Q1_2 V1_1 Q2N2907A
Q2 C1_1 Q2_2 0 Q2N2222
C1 C1_1 C1_2 20nF
R2 0 Q1_2 2.2meg
R1 C1_2 Q1_2 22k
.OP
.TRAN 1u 50m 0 1u
.lib eval.lib
.probe
.end

This circuit does not oscillate. V(C1_1) is 4.9504V, V(C1_2) is 5.293V,
VB(Q1) is 5.293V, VB(Q2) is 772.971mV. I(D1) = IC(Q2) = 89.884mA. I(C1) =0.
I think that IC(Q2) should discharge C1 but all the current goes through D1
instead.


I was wondering how this circuit is supposed to work, and what possible
changes I could make to the PSpice netlist to derive the correct results.

 

[Terry Pinnell]

I'm having trouble with a PSpice simulation for a relaxation oscillator
posted in a previous message on sci.electronics.basics: "PUT Oscillator?"

Terry Pinnell was able to model the oscillator succesfully, using the
following netlist:

This simulation works correctly for CircuitMaker (using
Spice3f5/XSpice). A picture of the results is at
http://www.terrypin.dial.pipex­.com/Images/Relaxation1.gif

zero: There's a typo in your URL; it should be
http://www.terrypin.dial.pipex.com/Images/Relaxation1.gif