How to build a simple LC oscillator

A phase shift oscillator using a regular low-cost transistor? Figure 2 shows it:

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

---

9V>-------+------+ | | | [1µH] [10K] | | +------+ | | | | C | +----+----B [1000pF] | | E | | | |2N3904| [0.1µF] | +------+ | | | | | [3K3] [3K3] [1000pF] | | | | GND>-+----+------+------+

Version 4 SHEET 1 880 680 WIRE 256 -80 32 -80 WIRE 448 -80 256 -80 WIRE 256 -32 256 -80 WIRE 448 -32 448 -80 WIRE 448 96 448 48 WIRE 560 96 448 96 WIRE 448 144 448 96 WIRE 560 144 560 96 WIRE 32 192 32 -80 WIRE 256 192 256 48 WIRE 384 192 256 192 WIRE 256 208 256 192 WIRE 256 208 160 208 WIRE 448 256 448 240 WIRE 560 256 560 208 WIRE 560 256 448 256 WIRE 160 272 160 208 WIRE 256 272 256 208 WIRE 448 272 448 256 WIRE 560 288 560 256 WIRE 32 384 32 272 WIRE 160 384 160 336 WIRE 160 384 32 384 WIRE 256 384 256 352 WIRE 256 384 160 384 WIRE 448 384 448 352 WIRE 448 384 256 384 WIRE 560 384 560 352 WIRE 560 384 448 384 WIRE 32 448 32 384 FLAG 32 448 0 SYMBOL ind 432 -48 R0 SYMATTR InstName L1 SYMATTR Value 1e-6 SYMBOL voltage 32 176 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL npn 384 144 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL cap 544 144 R0 SYMATTR InstName C2 SYMATTR Value 1000p SYMBOL cap 544 288 R0 SYMATTR InstName C1 SYMATTR Value 900p SYMBOL res 432 256 R0 SYMATTR InstName R1 SYMATTR Value 3,3k SYMBOL res 240 -48 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL res 240 256 R0 SYMATTR InstName R3 SYMATTR Value 3.3k SYMBOL cap 144 272 R0 SYMATTR InstName C3 SYMATTR Value .1e-6 TEXT 56 408 Left 0 !.tran .002 uic

JF

If you want a simple OSC and make your own coil, look at a Armstrong Oscillator.

That has what is called a tickler coil, another coil is wound on the same form as the feed back etc.. We use a armstrong variant osc that generates 100Khz at 250 K watts. It's all one tube!, Very simple.

"

A good healthy bypass cap from 9V to ground is probably essential -- John forgot to mention it because he bypasses _everything_ (I'm sure).

--
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

--
I\'m sure you didn\'t mean to say that I let everything go by unheeded, so
thanks for the kind words and yes, I mostly do. :-)

Not an excuse, but SPICE makes it so easy with wires that have no
inductance and voltage sources with zero output impedances that it\'s
easy to forget what\'s happening in the real world when working up a
circuit.

On the flip side of the coin, SPICE can model the real world if one can
define it.

Probably the best example of that is JT\'s success.

BTW, I have an unusual circuit which you might find interesting and
which might make us some money.

May I email it to you?

JF

I'm completely swamped with work that makes me money (thank goodness!), but send away if you can get the PCB to fit into an email (gawd I'm being a smartass tonight).

--
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

Thank you a lot, this is what I was looking for ! I'll try to build them tonight.

If you will be using this to drive digital circuitry, you can build simple RC oscillators with CMOS gates that have clean rectangular outputs. Requires 2 inverter stages (or NAND or NOR with appropriate inputs ties high/low), one C, and 1 or 2 Rs. See Don Lancaster's "CMOS Cookbook" page 225. (At least, it's page 225 in my ancient edition.)

In fact, if you have a Schmitt-trigger gate like a CD4093 you only need one gate: Tie one input high, put your C from the other input to ground, and the R from that input to the output. Simple!

Best regards,

Bob Masta DAQARTA v4.51 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Sound Level Meter FREE Signal Generator Science with your sound card!

I've just succeeded in building the phase-shift oscillator (fig. 2). I did it with a 2N2222 which seems to be almost the same as 2N3904, but the setting of R6 was quite subtle to make the circuit oscillate. I could finally probe the RC network with a scope and understand how it works !

I'll try John's circuit tomorrow.

AB

The hfe for the 2222 is quite poor at low currents, see if you have some small signal BC-type in your junk box. Those are more popular in Europe.

Hey, but at least it worked.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.