Amplify pulses without requiring high supply voltages

Thread Starter

ursonor99

Joined Jan 10, 2022
2
Hello , I was working on an idea , in which i was trying to produce pulses of voltages around +-25V and currents of 50mA . and was looking into ways to amplify the the signal generated by AD9833 (0-0.6V swing with 0.3v dc bias) to my desired outputs .
My first though was to use a step up transformer with a high current drive OP AMP source .
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So I have built this simulation which kind of works how i expect to , but the transformer behavior is extremely sensitive to the op amp and series resistance at primary etc .
Is there any better approach to do this ? or is the transformer the best option >
 

LowQCab

Joined Nov 6, 2012
1,614
What are You trying to build, and why did You choose the Parts that You have ?
What are the specs of the Load ?, and why such high Voltage/Current ?

A Transformer sounds like a crutch,
after You discovered that your Circuit doesn't provide what ever it is that You need for an output.
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Alec_t

Joined Sep 17, 2013
12,466
Welcome to AAC!
What is the purpose of U1?
Why does the V3 voltage have a DC offset when you are applying it to U1 via a capacitor?
Are you aware that a 741 will struggle to handle a 10kHz signal (though that may not be an issue if you are only using it as a unity-gain buffer)?
 

drjohsmith

Joined Dec 13, 2021
124
Welcome to AAC!
What is the purpose of U1?
Why does the V3 voltage have a DC offset when you are applying it to U1 via a capacitor?
Are you aware that a 741 will struggle to handle a 10kHz signal (though that may not be an issue if you are only using it as a unity-gain buffer)?
Me thinks your simulating using a perfect transformer
do you want a "sine wave" type pulse, or a more squared one.
 

Thread Starter

ursonor99

Joined Jan 10, 2022
2
Welcome to AAC!
What is the purpose of U1?
Why does the V3 voltage have a DC offset when you are applying it to U1 via a capacitor?
Are you aware that a 741 will struggle to handle a 10kHz signal (though that may not be an issue if you are only using it as a unity-gain buffer)?
What are You trying to build, and why did You choose the Parts that You have ?
What are the specs of the Load ?, and why such high Voltage/Current ?

A Transformer sounds like a crutch,
after You discovered that your Circuit doesn't provide what ever it is that You need for an output.
.
.
.
First of all thank you for replying everyone !!
I came across a TENS electrical muscle stimulation unit that i found interesting and hence was trying to design something myself that behaved similarly . these stimulation are done at those voltage levels and current . but the pulses are very short duration and hence low avg power .

The U1 was intended as a voltage follower to prevent the loading effect on the high pass filter .
V3 is used to replicate the signal generated by the DDS signal generator AD9833


The two approaches i was able to think of are 1. using a high voltage op amp but that means the supply voltage , 2. using a high current op amp with low supply voltage .
I though 2nd approach was more suitable for a battery powered setup as it will simplify the power supply stage


Me thinks your simulating using a perfect transformer
do you want a "sine wave" type pulse, or a more squared one.
yes i used a ideal transformer here coz the transformer datasheets didn't give me a clear idea about the impedance and inductance . so i took the turn ratio i wanted and created a ideal transformer to see if the idea will work .
I am trying to keep the shape of sine in output .
for square pulses i came across few circuits where they were trying to drive transformer with a mosfet .
 

Alec_t

Joined Sep 17, 2013
12,466
Are you absolutely certain that 50mA isn't a dangerous level for a TENS device? Some people may be particularly susceptible to this level.
Which components are you relying on to limit the current to a safe level?
 

LowQCab

Joined Nov 6, 2012
1,614
1)
It's a bad idea to build your own Medical-Device.

2)
TENS Devices are readily available for sale to the public.

3)
You provided no means for adjusting Frequency, Voltage, or limiting Current.
The Voltage and Current requirements will vary wildly depending upon
Electrode placement, efficacy of the Conductive-Goop used, personal tolerances, etc..

4)
A TENS-Device produces a chain of extremely sharp, short, Voltage-Spikes, not a Sine-Wave.

5)
I considered creating a Schematic for You, but decided it would be a bad idea,
there are too many things that could easily go wrong.
And, aside from that, A TENS-Device merely temporarily takes "some" of the edge off of pain.
The source of the pain needs to be repaired, not covered-up.

6)
Go find a good Chiropractor.
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