Schmitt Trigger with Constant Current Source.

Thread Starter

Prasanna K Routray

Joined Sep 17, 2015
21
Hi All,
To realise the below circuit I designed a circuit in MultiSim and tried ti simulate. But I'm unable to do so. I would appreciate any help in this regard.
1624971896198.png
1624971846497.png
 

Thread Starter

Prasanna K Routray

Joined Sep 17, 2015
21
Hi bertus,
Thanks for the quick response but if I remove the feedback how can I use the feedback?

The SPDT switch has to be controlled automatically because of the voltage swing by Schmitt Trigger.

If you could tell me how to solve the problem or any suggestion.
 

crutschow

Joined Mar 14, 2008
28,227
In the original schematic, the line from the output to the switch is not a connection, it indicates that the output state is controlling the position of the switch.
You need to change your schematic to reflect that.
 

bertus

Joined Apr 5, 2008
21,683
Hello,

The feedback for the switch should come from the output of the inverter.
You have connected it at the input of the inverter.

Bertus
 

Thread Starter

Prasanna K Routray

Joined Sep 17, 2015
21
In the original schematic, the line from the output to the switch is not a connection, it indicates that the output state is controlling the position of the switch.
You need to change your schematic to reflect that.
Hi, Thanks for the reply.
Can you please help me in drawing the schematic because even after looking for a circuit I could not find any. I may be using inappropriate keywords while searching on the internet. I would appreciate your suggesation.
 

bertus

Joined Apr 5, 2008
21,683
Hello,

Again you have shorted the in and output of the inverter.
Remove that connection and connect the output of the inverter to the control input of S1.

Bertus
 

Alec_t

Joined Sep 17, 2013
12,321
I don't see any any triangular wave from that circuit (using generic NPN and PNP), Eric? LTS is telling me vc rises to ~3.4V and stays there.
 

crutschow

Joined Mar 14, 2008
28,227
What is the polarity of the S1 control input versus the position of the S1 wiper?

Try interchanging the two control inputs (U3A output to - and ground to +).
 
Last edited:

ericgibbs

Joined Jan 29, 2010
14,245
hi PKR,
Your post #14, simulation voltages are not the same as my posted sim.
You are using a +/-15V supply on the OPA, my circuit uses a single +5V supply
How do you expect the Current Mirrors to work correctly as they are only powered by +5V., when subject to a +/-15V control voltage.?

Also what are the specifications of the 4 transistors.?

E
 

ericgibbs

Joined Jan 29, 2010
14,245
hi Alec,
I do not use the Generic transistors in my sims. never sure about their claimed performance, had some problems in past using the generics.
Prefer to use known types, same applies to the MOSFET's.

E
 

Alec_t

Joined Sep 17, 2013
12,321
Likewise, Eric. However, your post #10 circuit shows R4 input as vc, not vc2. The generic transistors work fine in your circuit if R4 input is vc2.
 

Thread Starter

Prasanna K Routray

Joined Sep 17, 2015
21
hi PKR,
Your post #14, simulation voltages are not the same as my posted sim.
You are using a +/-15V supply on the OPA, my circuit uses a single +5V supply
How do you expect the Current Mirrors to work correctly as they are only powered by +5V., when subject to a +/-15V control voltage.?

Also what are the specifications of the 4 transistors.?

E
I modified the supply and changed the transistors also. Still unable to simulate.
1625062421896.png
 
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