unijunction equivalent circuit?

Aug 29, 2013 5 Replies
J

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) +r*57)/7,q=q?q-1?q-2?1-p%79?-1:0:p%79-77?1:0:p158?-79:0,q?!a[p+q*2 ]?a[p+=a[p+=q]=q]=q:0:0;for(;q++-1817;)printf(q%79?"%c":"%c\n"," #"[!a[q-1]]);}
Vote
Twitter Facebook LinkedIn
J

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 | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Vote
Twitter Facebook LinkedIn
J

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 | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Vote
Twitter Facebook LinkedIn
N

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

If a PUT works, try:

formatting link

Steve

Vote
Twitter Facebook LinkedIn
J

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.

Vote
Twitter Facebook LinkedIn
S

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

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required