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[SOLVED] Practical circuit problems

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jake14

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hello, i m a first year student in electronic.
i tried to make a experiment in "push pull inverter" and it worked in simulation (software ltspice) but when i tried a practical exemple it failed
24879166_10208283034633400_1012088657_o.png
 

I am not sure, but the max DC current for this transistor is 0.5A. The RMS value of that I(C1) is about 2.47A. Maybe it is a reason.
 

I did not notice,thank you.
I have irf510 and bs270 at my disposal right now which one you suggest?
 

BS270's max continuous current is smaller, try with IRF510. But if this I(C1) is the current of the capacitor in the LC tank, maybe the transistors have got smaller drain current with a factor of Q.
I would measure the DC and AC current consumption of the branches without the LC tank first, then with the LC.
...and obviously simulate it with the new transistor first of all. In simulation add some series parasitic resistance to the inductor.
 

i m sorry but i did not understand you explanation .
if you can rephrase that i would be thankful.
 

Simulate the circuit with IRF510. Check the drain currents of the transistors. Under oscillation, the RMS value of the drain currents shouldn't be higher than max. continuous DC current by the datasheet of the transistor. And you simulated with ideal elements. But in reality the inductor has got a significant series resistance. Add some resistance in series with the inductors to model the loss of them.
 

I did the simulation

1.0.png

but i received a erreur message

1.png

edit:
I tried with irf510 but because it is not a mosfet transistor it caused some problems in the simulation then I did a simulation with irf3708, which gives in the datasheet a drain current about 30 amper on vgs=2.7 v.
 
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I tried with irf510 but because it is not a mosfet transistor it caused some problems in the simulation then I did a simulation with irf3708, which gives in the datasheet a drain current about 30 amper on vgs=2.7 v.
IRF510 is a MOS transistor, what are you talking about? All transistors which start with IRF are MOSFETs.
**broken link removed**
 

As i similate the gate voltage of py circuit is a round 5.4v On the datasheet of irf 510 the dran current around 1p for vgs =5v
Then when i simulate Some errors comes on simulation I change to irf3708 I want to see if its adequated to the circuit or can you please propose new mosfet to buy.In reality i need helps because i dont have a good background on Electronic.
 

Hi,

On the datasheet of irf 510 the dran current around 1p for vgs =5v
Where did you find this information? Are you sure you read the IRF510 datasheet?

Klaus
 

Looks like you created your own subcircuit for your transistors, which is an option, but LTspice includes many common FETs in their default libraries. Go to the Component menu in the toolbar, select "nmos," and place on your schematic. Then right click the nmos symbol on the schematic and click "pick new MOSFET." You'll get a list of models, including IRF510 and IRF530.
 

Hello
i change the mosfets to irf510 When the experiments run The outputs are not as in the simulation And the gate driver voltage is zero.
I think that maybe the coils are not well chosen.
can any one suggest a kind of coil that can be used with push pull inverter.
 

The circuit looks like it was designed for bipolar transistors rather than MOSFETs but in any case the inductor seems to be far too small in value when shunted by 5uF.

The coils should be the center tapped primary of the transformer with the load on the secondary. If you are simulating as two independent coils it will not work properly.

Brian.
 

It worked for him with BS170 MOSFET in the simulation. Without center tapped transformer I think.
 

hello,
I have tried with 749196321 transformer
But the output seen in the circuit is a round 500 mv and for even very high frequency
i dont know what to do
.
 

Show the waveforms. Drain currents, drain and gate voltages, parameters of that transformer and your currently used schematic. Maybe somebody will know, but share more details.
 

5KHz is a little low for that transformer but I am still suspicious of the whole thing. You are never going to get high power from it with 50 Ohm source resistors as they limit the theoretic maximum to about 2.8W. If you want maximum output it would be more sensible to hard drive the MOSFETs rather than use RC networks in the feedback and even at 5KHz I would guess 5uF across the output is going to sink most of the output.

What frequency is it supposed to run at? How much output are you expecting from it?

Brian.
 

I would guess 5uF across the output is going to sink most of the output.

I don't understand this, why it would sink the output? 5uF is the capacitor of the LC tank, all current of the C flow through the L too. L is coupled to the resistive load by a transformer, so if the current of C is larger, the L current too, and load current should be higher too.
 

1/(2 * pi * sqrt( L * C)) will explain. Try inserting 5KHz (from the simulation trace) and the inductance of the transformer.

Brian.
 

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