unijunction equivalent circuit?

So is there any simple circuit using conventional NPN and PNP transistors?

I've seen this circuit

formatting link
in _Sourcebook of Electronic Circuits_, but it doesn't really work- it latches but does not release when used in a relaxation oscillator. Perhaps it did work with lower gain transistors.

--
/*  jhallen@world.std.com AB1GO */                        /* Joseph H. Allen */ 
int a[1817];main(z,p,q,r){for(p=80;q+p-80;p-=2*a[p])for(z=9;z--;)q=3&(r=time(0) 
 Click to see the full signature
Reply to
Joseph H Allen
Loading thread data ...

You need at least one Vbe resistor (on the NPN) to establish a holding current trip point. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
 Click to see the full signature
Reply to
Jim Thompson

A quick surf produces this....

  • formatting link
* *Default N-Channel Unijunction Transistor .SUBCKT XUJT 1 2 3 DE 1 4 EMITTER VE 4 5 DC 0 HVE 6 0 VE 1K RVE 0 6 1MEG BBB 5 7 I=0.00028*V(5,7)+0.00575*V(5,7)*V(6) CBB 5 7 35P ***RB1 7 2 38.15 RMOD ***RB2 3 5 2.518K RMOD RB1 7 2 RMOD 38.15 RB2 3 5 RMOD 2.518K .MODEL RMOD R TC1=.01 .MODEL EMITTER D (IS=21.3P N=1.8) .ENDS XUJT

  • Motorola IP=.5U IV=6M VB1(sat)=3 Rbb=6.1K Vob1=3.6: E, B1, B2 .SUBCKT X2N2646 1 2 3 DE 1 4 EMITTER VE 4 5 DC 0 HVE 6 0 VE 1K RVE 0 6 1MEG BBB 5 7 I=0.00028*V(5,7)+0.00575*V(5,7)*V(6) CBB 5 7 35P

***RB1 7 2 38.15 RMOD ***RB2 3 5 2.518K RMOD RB1 7 2 RMOD 38.15 RB2 3 5 RMOD 2.518K .MODEL RMOD R TC1=.01 .MODEL EMITTER D (IS=21.3P N=1.8) .ENDS X2N2646

This is in B-source notation. In your Spice variant you may need to replace BBB with GVALUE notation. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
 Click to see the full signature
Reply to
Jim Thompson

Can you use a pseudo PUT or do you need a UJT?

If a PUT works, try:

formatting link

Steve

Reply to
NO SPAM Steve

On a sunny day (Thu, 29 Aug 2013 22:34:19 +0000 (UTC)) it happened snipped-for-privacy@TheWorld.com (Joseph H Allen) wrote in :

I dunno but I have a bunch of 2N2646 UJTs from ebay for cheap. Those work OK.

Reply to
Jan Panteltje

You need to keep the value of (RB1 || RB2)

Reply to
Spehro Pefhany

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.