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Trouble simulating a Wein Bridge Oscillator in LTspice

I'm trying to simulate a Wein Bridge Oscillator in LTspice (I'm new to it), and haven't managed to get it to work. I've simulated a few other oscillators without any problems, but for some reason this one is not oscillating. Maybe it has something to do with the way I set up the op amp (or the one I selected)? Below is the .asc file I've used to put it together. Any insight is greatly appreciated!

Thanks! Dave

Version 4 SHEET 1 928 680 WIRE 48 -320 -64 -320 WIRE 176 -240 48 -240 WIRE 64 -208 -144 -208 WIRE -144 -192 -144 -208 WIRE 64 -192 64 -208 WIRE -64 -176 -64 -320 WIRE 32 -176 -64 -176 WIRE 176 -160 176 -240 WIRE 176 -160 96 -160 WIRE 32 -144 -16 -144 WIRE 64 -80 64 -128 WIRE 176 -80 176 -160 WIRE -144 -64 -144 -112 WIRE 176 32 176 0 WIRE -16 112 -16 -144 WIRE 176 112 176 96 WIRE 176 112 -16 112 WIRE 176 128 176 112 WIRE -16 144 -16 112 WIRE -16 240 -16 208 WIRE 80 240 -16 240 WIRE 176 240 176 208 WIRE 176 240 80 240 WIRE 80 272 80 240 FLAG -144 -64 0 FLAG 64 -80 0 FLAG 80 272 0 SYMBOL voltage -144 -208 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 0 -66 54 Left 0 WINDOW 3 47 51 Left 0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL res 32 -336 R0 SYMATTR InstName R1 SYMATTR Value 20k SYMBOL cap 160 32 R0 SYMATTR InstName C1 SYMATTR Value .01=B5 SYMBOL res 160 112 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL cap -32 144 R0 SYMATTR InstName C2 SYMATTR Value .01=B5 SYMBOL res 160 -96 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL Opamps\\\\LT1024 64 -224 R0 SYMATTR InstName U1 TEXT -104 -360 Left 0 !.tran 0 .005 0 .000001 startup

Reply to
dave.harper
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"dave.harper" schrieb im Newsbeitrag news: snipped-for-privacy@q18g2000vbn.googlegroups.com... I'm trying to simulate a Wein Bridge Oscillator in LTspice (I'm new to it), and haven't managed to get it to work. I've simulated a few other oscillators without any problems, but for some reason this one is not oscillating. Maybe it has something to do with the way I set up the op amp (or the one I selected)? Below is the .asc file I've used to put it together. Any insight is greatly appreciated!

Thanks! Dave

Hello Dave,

When you run circuits with single supply, you jave to choose the right opamp and you have to provide a reference to VCC/2. Please try my example below.

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Best regards, Helmut

Version 4 SHEET 1 928 680 WIRE 176 -480 128 -480 WIRE 272 -480 240 -480 WIRE 128 -400 128 -480 WIRE 176 -400 128 -400 WIRE 272 -400 272 -480 WIRE 272 -400 240 -400 WIRE -128 -304 -160 -304 WIRE -16 -304 -48 -304 WIRE 16 -304 -16 -304 WIRE 128 -304 128 -400 WIRE 128 -304 96 -304 WIRE 160 -304 128 -304 WIRE 272 -304 272 -400 WIRE 272 -304 240 -304 WIRE 96 -192 96 -208 WIRE -16 -176 -16 -304 WIRE 64 -176 -16 -176 WIRE 224 -160 128 -160 WIRE 272 -160 272 -304 WIRE 272 -160 224 -160 WIRE 64 -144 -16 -144 WIRE 272 -112 272 -160 WIRE -384 -80 -384 -128 WIRE -336 -80 -384 -80 WIRE -224 -80 -256 -80 WIRE -144 -80 -144 -128 WIRE -144 -80 -224 -80 WIRE 96 -80 96 -128 WIRE -144 -48 -144 -80 WIRE -384 -32 -384 -80 WIRE -224 -32 -224 -80 WIRE 272 16 272 -32 WIRE -384 80 -384 48 WIRE -224 80 -224 48 WIRE -144 80 -144 16 WIRE -16 112 -16 -144 WIRE 112 112 -16 112 WIRE 272 112 272 80 WIRE 272 112 112 112 WIRE 272 128 272 112 WIRE -16 144 -16 112 WIRE -16 240 -16 208 WIRE -16 240 -112 240 WIRE 272 240 272 208 WIRE 272 240 -16 240 FLAG -384 80 0 FLAG 96 -80 0 FLAG -384 -128 +5V FLAG 96 -208 +5V FLAG -112 240 +2.5V FLAG -160 -304 +2.5V FLAG 112 112 in1 FLAG 224 -160 out FLAG -144 80 0 FLAG -224 80 0 FLAG -144 -128 +2.5V SYMBOL voltage -384 -48 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 WINDOW 0 -66 54 Left 0 WINDOW 3 47 51 Left 0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL res 0 -288 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R1 SYMATTR Value 12k SYMBOL cap 256 16 R0 SYMATTR InstName C1 SYMATTR Value .01µ SYMBOL res 256 112 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL cap -32 144 R0 SYMATTR InstName C2 SYMATTR Value .01µ SYMBOL res 256 -128 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL Opamps\\\\LT1797 96 -224 R0 SYMATTR InstName U3 SYMBOL res -144 -288 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL res 144 -288 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL diode 176 -384 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D1 SYMATTR Value 1N4148 SYMBOL diode 240 -496 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL res -352 -64 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R6 SYMATTR Value 1k SYMBOL res -240 -48 R0 SYMATTR InstName R7 SYMATTR Value 1k SYMBOL polcap -160 -48 R0 SYMATTR InstName C3 SYMATTR Value 10µ TEXT -440 -464 Left 0 !.tran 0 10m 0 1u TEXT -440 -424 Left 0 !.ic V(in1)=2.7 TEXT -440 -512 Left 0 ;Wien Oscillator With Single Supply

Reply to
Helmut Sennewald

Disconnect the connection from the RC network to the voltage amplifier input (or output). Inject a signal into the amplifier input (or the network input), and look at the signal that comes out of the network (or amplifier).

If you do a frequency sweep of the linearized system, you should see a point where the phase shift is close to zero and the gain is greater than

0dB. If you don't see this, there's no chance of getting oscillation.

So if you're not getting gain > 0dB, and if it's not occurring close to the 0 degree phase shift point, then you have problems with your circuit, and you need to get to work.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

- snipped-for-privacy@q18g2000vbn.googlegroups.com...

Fantastic, thanks! It works like a charm. I'll be studying this and probably breadboarding it tonight.

Thanks for the help! Dave

Reply to
dave.harper

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