A ngspice Circuit using LM358

• NI, INV, POS, NEG, OP X1 1 2 3 4 5 LM358/NS Vp1 3 0 5V Vn1 4 0 0V R1 5 2 0.1 *Short circuit from o/p to inv Vsource 1 0 sin(0 1 625) *to be replaced with current source

The LM358 can't swing below ground on single supplies -- feed it -5v for Vn1.

-- Cheers, James Arthur

I tried that. Doesn't help. One can also try with a DC bias to the first stage input. Say a 2.5V DC bias "Vsource 1 0 sin(2.5 1 625)". This doesn't help too.

Infact, its not the first stage LM358 output (this is simulated correctly). Its the node after the LM358 output, the one at the capacitor "output" (node 6) which I find erroneous.

I was hoping that someone simulates this circuit with another Spice software and cross-verifies the behaviour.

Thanks for looking into it, Anand

Here's an ACSII version of what I understand your circuit to be: (view in a fixed font, such as Courier)

Vp1 =3D 5v -+- |\ | Vp2 =3D 5v | \3 -+- Vin>---1-|+ \ C1 |\ |

This circuit has several problems--I already pointed out one. If you're going to feed it a.c. you need dual supplies or the 1st stage will clip.

The input to the 2nd stage outputs a bias current. You need to dispose of that current, such as with a feedback resistor or a resistor to some d.c. voltage.

Last, the coupling capacitor is absurdly low--you might want to consider what you really want it to do.

-- Cheers, James Arthur

A simulator in the hands of someone with no basic electronic skills ?:-) ...Jim Thompson

That covers way too many people on the sci.electronics.* newsgroups, Jim. :(

he

Hey, we all gotta start somewhere.... :-)

-- Cheers, James Arthur

As much as I now use simulators, I would still argue that you should learn how to do everything by hand/pencil/paper before going on to using simulators. ...Jim Thompson

On Tue, 03 May 2011 10:13:33 +0530, "Anand P. Paralkar" wrote:

--- Please don't top post.

Offset the buffer's + input to 2.5V with a fairly high resistance voltage divider and cap-couple the + input to the source.

On the E-to-I converter, use another divider on the + input to get the offset, and DC couple the - input to the buffer output and to its own output through equal value resistors.

Like this, using LTspice:

Version 4 SHEET 1 880 680 WIRE 64 32 -112 32 WIRE 208 32 64 32 WIRE 336 32 208 32 WIRE 528 32 336 32 WIRE 64 48 64 32 WIRE 336 48 336 32 WIRE 256 80 160 80 WIRE 544 80 464 80 WIRE 640 80 624 80 WIRE 208 112 208 32 WIRE 160 128 160 80 WIRE 176 128 160 128 WIRE 528 128 528 32 WIRE 256 144 256 80 WIRE 256 144 240 144 WIRE 368 144 256 144 WIRE 464 144 464 80 WIRE 464 144 448 144 WIRE 496 144 464 144 WIRE 64 160 64 128 WIRE 64 160 48 160 WIRE 80 160 64 160 WIRE 176 160 80 160 WIRE 640 160 640 80 WIRE 640 160 560 160 WIRE 672 160 640 160 WIRE 336 176 336 128 WIRE 496 176 336 176 WIRE 80 208 80 160 WIRE 336 208 336 176 WIRE -112 224 -112 32 WIRE -16 224 -16 160 WIRE -112 336 -112 304 WIRE -16 336 -16 304 WIRE -16 336 -112 336 WIRE 80 336 80 288 WIRE 80 336 -16 336 WIRE 208 336 208 176 WIRE 208 336 80 336 WIRE 336 336 336 288 WIRE 336 336 208 336 WIRE 528 336 528 192 WIRE 528 336 336 336 WIRE -112 400 -112 336 FLAG -112 400 0 FLAG 672 160 OUT SYMBOL Opamps\\LT1001 208 80 R0 SYMATTR InstName U1 SYMBOL voltage -16 208 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 1 1000) SYMBOL voltage -112 208 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 5 SYMBOL cap 48 144 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 1E-6 SYMBOL res 48 32 R0 SYMATTR InstName R1 SYMATTR Value 100K SYMBOL res 64 192 R0 SYMATTR InstName R2 SYMATTR Value 100K SYMBOL Opamps\\LT1001 528 96 R0 SYMATTR InstName U2 SYMBOL res 320 32 R0 WINDOW 0 -42 55 Left 0 WINDOW 3 -57 24 Left 0 SYMATTR InstName R3 SYMATTR Value 100K SYMBOL res 320 192 R0 SYMATTR InstName R4 SYMATTR Value 100K SYMBOL res 464 128 R90 WINDOW 0 -31 58 VBottom 0 WINDOW 3 -31 60 VTop 0 SYMATTR InstName R5 SYMATTR Value 10K SYMBOL res 640 64 R90 WINDOW 0 -28 55 VBottom 0 WINDOW 3 -31 54 VTop 0 SYMATTR InstName R6 SYMATTR Value 10K TEXT -106 368 Left 0 !.tran 10E-3

-- JF

On Tue, 03 May 2011 14:30:12 -0500, John Fields wrote:

--- Delete the second divider and connect the buffer + input to the I-to-E

• input if you want a DC output in phase with the AC input, and if you want an ac output in phase with the AC input:

Version 4 SHEET 1 880 680 WIRE 64 32 -112 32 WIRE 208 32 64 32 WIRE 448 32 208 32 WIRE 64 48 64 32 WIRE 256 80 160 80 WIRE 464 80 400 80 WIRE 560 80 544 80 WIRE 208 112 208 32 WIRE 160 128 160 80 WIRE 176 128 160 128 WIRE 448 128 448 32 WIRE 256 144 256 80 WIRE 256 144 240 144 WIRE 288 144 256 144 WIRE 400 144 400 80 WIRE 400 144 368 144 WIRE 416 144 400 144 WIRE 64 160 64 128 WIRE 64 160 48 160 WIRE 80 160 64 160 WIRE 160 160 80 160 WIRE 176 160 160 160 WIRE 560 160 560 80 WIRE 560 160 480 160 WIRE 416 176 400 176 WIRE 80 208 80 160 WIRE 160 208 160 160 WIRE 400 208 400 176 WIRE 400 208 160 208 WIRE -112 224 -112 32 WIRE -16 224 -16 160 WIRE -112 336 -112 304 WIRE -16 336 -16 304 WIRE -16 336 -112 336 WIRE 80 336 80 288 WIRE 80 336 -16 336 WIRE 208 336 208 176 WIRE 208 336 80 336 WIRE 448 336 448 192 WIRE 448 336 208 336 WIRE -112 400 -112 336 FLAG -112 400 0 FLAG 624 160 OUT SYMBOL Opamps\\LT1001 208 80 R0 SYMATTR InstName U1 SYMBOL voltage -16 208 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 1 1000) SYMBOL voltage -112 208 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 5 SYMBOL cap 48 144 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 1e-6 SYMBOL res 48 32 R0 SYMATTR InstName R1 SYMATTR Value 100K SYMBOL res 64 192 R0 SYMATTR InstName R2 SYMATTR Value 100K SYMBOL Opamps\\LT1001 448 96 R0 SYMATTR InstName U2 SYMBOL res 384 128 R90 WINDOW 0 -31 58 VBottom 0 WINDOW 3 -31 60 VTop 0 SYMATTR InstName R5 SYMATTR Value 10K SYMBOL res 560 64 R90 WINDOW 0 -28 55 VBottom 0 WINDOW 3 -31 54 VTop 0 SYMATTR InstName R6 SYMATTR Value 10K SYMBOL cap 624 144 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C2 SYMATTR Value 1e-6 TEXT -106 368 Left 0 !.tran 10E-3

-- JF

I meant most of us weren't born knowing electronics, not that simulators were the best teachers.

Pffft....BANG! is one of the best teachers.

-- Cheers, James Arthur

Certainly! But I learned on tubes (valves for those on the other side of the pond), so I had no destruction episodes, other than an occasional resistor that emitted smoke :-) ...Jim Thompson

Kind of reminds me of when RAD, Java /JavaScript, PHP and related things came along. Young people called themselves computer programmers! WOW

I think many of those have really forgotten or never knew what real programming is all about..

Jamie

You mean you never got a horizontal sweep tube pressed into 40 meter service so hot the glass got sucked onto the plate before it went whizz-bang?

Jim

Sure

Made a CB amp years ago for the car using a pair of 6jS6 es....

some Radio shaft power transformers turned around backwards for an inverter with a multiplier rectifier for the B+///it got warm in the car after a while..

Jamie

No. Most of us know how to use a tube without melting the glass.

I used to tune up the bias on my KT88's by watching for plate glow :-) ...Jim Thompson

I used more ceramic or metal jacketed tubes for high power applications. The only melted glss tubes I've seen were in color TVs. If a 4CX250 is glowing, it's already bad. The same goes for 65 KW Klystrons.