Hello everyone,

now i want to use THS4521 as amplifier and gain is 2. I have designed the circuit in LTSpice as the data sheet, but it didn't work.
Even worse, there is no signal at the output after the simulation. I don't know why.
If anyone knows, can you give me some advice to correct it? Thanks in advance!
Attached is my circuit in LTSpice.

Jackie

 

I see no AC signal source and no simulation commands.

 

I see no AC signal source and no simulation commands.

As this figure, the input is 1V and the output "diffl+" should be 2V, because the gain of this amplifier is 2. But now the result is strange. I don't know what's the problem of the design.

 

Here's a better copy of what the circuit should look like. If I'm not mistaken the input will require a DC path to ground. Either through the input voltage source or a resistor. You didn't mention if the input was a DC or AC signal.
Steve G

 

Your output is in KV so obviously, the circuit is not connected correctly or the model is not correct.

Please redraw the circuit in a more conventional and less convoluted fashion with a minimum of jogs in the wires.
It's very hard to follow all the jogs and angles in the circuit, the way it's drawn.
Look at how a standard circuit is drawn, if you don't understand how to do it.
I know it takes a little extra work to draw the schematic properly but that's a normal part of the process.

 

Your output is in KV so obviously, the circuit is not connected correctly or the model is not correct.

Please redraw the circuit in a more conventional and less convoluted fashion with a minimum of jogs in the wires.
It's very hard to follow all the jogs and angles in the circuit, the way it's drawn.
Look at how a standard circuit is drawn, if you don't understand how to do it.
I know it takes a little extra work to draw the schematic properly but that's a normal part of the process.

Now i have redrawed the component and it looks like a standard component. But it didn't work too, there is now even no signal at the output.
I think i have right drawed the component. What is the prolem?
Attached is my new circuit. Thanks.

 

Here's a better copy of what the circuit should look like. If I'm not mistaken the input will require a DC path to ground. Either through the input voltage source or a resistor. You didn't mention if the input was a DC or AC signal.
Steve G

View attachment 143607

Thanks for your advice. As #6 i have redrawed the component and the circuit. Do you know why i can't get signal at output? The question and the files are the same as #6.

 

Where happened to the designation number for the amp and its model file?
All I see is a generic amp symbol.

 

I don't know why you can't get the signal out in simulation. I don't use LTSpice or simulators. I breadboard with real components.
Steve G

 

Where happened to the designation number for the amp and its model file?
All I see is a generic amp symbol.

Thanks for your answer.
I designed the pin number is like data sheet as below.

And the library file is download from the spice homepage of TI as attached. I think the both have already matched. But i don't know why it did not works.

 

And the library file is download from the spice homepage of TI as attached. I think the both have already matched. But i don't know why it did not works.

Thinking they are matched is not sufficient.
You need to check that the pin numbers in the symbol actually correspond to the signal numbers in the model and, if not, correct them.
If they don't match, that would explain why you have no signal.

And please don't post .rar files.
I don't open them.

 

Thinking they are matched is not sufficient.
You need to check that the pin numbers in the symbol actually correspond to the signal numbers in the model and, if not, correct them.
If they don't match, that would explain why you have no signal.

And please don't post .rar files.
I don't open them.

I have checked the pin number and they are matched. So i don't know what is wrong. Attached are all my circuit and needed files.

 

No, the pins are not matched.
How did you check them?
For example the Vin+ input is netlist pin 8 on the symbol (right click on the pin, below)


whereas it is actually netlist number 5 (VINP) as shown below.

.subckt THS4521 VOUTM VOUTP VOCM VINM VINP VEE VCC PD

You need to correct the pin number order on the symbol.

 

No, the pins are not matched.
How did you check them?
For example the Vin+ input is netlist pin 8 on the symbol (right click on the pin, below)
View attachment 143631

whereas it is actually netlist number 5 (VINP) as shown below.

.subckt THS4521 VOUTM VOUTP VOCM VINM VINP VEE VCC PD

You need to correct the pin number order on the symbol.

Thanks for your help.
I have corrected the pin number as you given. Where did you find this pin order?
Because now there is signal at the output. But the output is still strange.My goal is to make the gain of the amplifier is 2. Is there a error with my design circuit?

 

anyone has the pspice correct model?