I am trying to use the TLV2241 DIP package IC to make a relaxation oscillator(square wave oscillator using positive feedback). I first simulated the design in spice (both ORCAD PSPICE and WINSPICE). I used the SPICE model of the TLV2241 provided in the data sheet provided by TI.COM . Please see the spice circuit file below.
Problem: In the simulated version I get an oscillation period of approx
6.2ms. However when I built the circuit using the chip I actually got a frequency of 19Hz(Period approx 52ms) I have made sure that all components are close to the specs as specified in the spice simulation Question) Is the model provided by TI, as shown below, adequate to accurately model the opamp. Please suggest why is there such a disparity between spice simulation(s) and the actual circuit? Thanks SPICE CIRCUIT FILE FOR SQUARE WAVE GENERATOR USING TLV2241----------------------------------------------------------
*Relaxation oscillator using a single supply opamp- connections: non-inverting input
- | inverting input
- | | positive power supply
- | | | negative power supply
- | | | | output
- | | | | | ..SUBCKT TLV2241 1 2 3 4 5 C1 11 12 9.8944E-12 C2 6 7 30.000E-12 CEE 10 99 8.8738E-12 DC 5 53 DY DE 54 5 DY 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 61.404E6 -1E3 1E3 61E6 -61E6 GA 6 0 11 12 1.0216E-6 GCM 0 6 10 99 10.216E-12 IEE 10 4 DC 54.540E-9 IOFF 0 6 DC 5E-12 HLIM 90 0 VLIM 1K Q1 11 2 13 QX1 Q2 12 1 14 QX2 R2 6 9 100.00E3 RC1 3 11 978.81E3 RC2 3 12 978.81E3 RE1 13 10 30.364E3 RE2 14 10 30.364E3 REE 10 99 3.6670E9 RO1 8 5 10 RO2 7 99 10 RP 3 4 1.4183E6 VB 9 0 DC 0 VC 3 53 DC .88315 VE 54 4 DC .88315 VLIM 7 8 DC 0 VLP 91 0 DC 540 VLN 0 92 DC 540 ..MODEL DX D(IS=800.00E-18) ..MODEL DY D(IS=800.00E-18 RS=1M CJO=10P) ..MODEL QX1 NPN(IS=800.00E-18 BF=27.270E21) ..MODEL QX2 NPN(IS=800.0000E-18 BF=27.270E21) ..ENDS
XOP1 3 1 4 0 2 TLV2241 Cout 2 6 0.033uF RF 1 6 9.99K CF 1 0 10uF R2 6 3 1.001K R1 3 0 19.97K VS1 4 0 5V ..TRAN 0.01ms 100ms ..PROBE ..PLOT TRAN V(2) ..END