Op Amp Help

[tom_pay]

Hi Everyone,

I am trying to make a small amplifier for low-ish frequencies. 10 to 800 Hz.

I was planning to use a LM380 amplifier IC. However I have come across some problems.

1) What is the 'Bypass' pin? Do I need to put a capacitor on it?

2) What size AC coupling capacitor (on the input) should I use? Is there anything to govern this?

3) Can I put an AC input into the IC's input? The circuit only has single power supply (0 - 10v)

4) The IC has a fixed gain. I am only using the non-inverting input. What should I do with the inverting input? Do I let it float?

Thank you so much; in advanced. I'm sure that these questions are so simple and I'm just missing something. I'm so sorry.

Tom

 

[ericgibbs]

Hi Everyone,

I am trying to make a small amplifier for low-ish frequencies. 10 to 800 Hz.

I was planning to use a LM380 amplifier IC. However I have come across some problems.

1) What is the 'Bypass' pin? Do I need to put a capacitor on it?

2) What size AC coupling capacitor (on the input) should I use? Is there anything to govern this?

3) Can I put an AC input into the IC's input? The circuit only has single power supply (0 - 10v)

4) The IC has a fixed gain. I am only using the non-inverting input. What should I do with the inverting input? Do I let it float?

Thank you so much; in advanced. I'm sure that these questions are so simple and I'm just missing something. I'm so sorry.

Tom

hi Tom,
Do yo have this LM380 app note pdf.?

 

[tom_pay]

Hi

Yes, I have got that document. Unfortunately I cannot make any sense of it. I'm still stuck. Sorry!

Tom

 

[ericgibbs]

Hi Everyone,

I am trying to make a small amplifier for low-ish frequencies. 10 to 800 Hz.

I was planning to use a LM380 amplifier IC. However I have come across some problems.

1) What is the 'Bypass' pin? Do I need to put a capacitor on it?
Look at image1, it decoupling for the input stage, the value of the decoupling cap determines the power line noise freq/attenuation

2) What size AC coupling capacitor (on the input) should I use? Is there anything to govern this?
The input impedance is quoted a 150K, so if a input capacitor is used the required operating frequency range of the amp will set its value.

3) Can I put an AC input into the IC's input? The circuit only has single power supply (0 - 10v)
Yes, you require an input capacitor

4) The IC has a fixed gain. I am only using the non-inverting input. What should I do with the inverting input? Do I let it float?
The datasheet says it can be left disconnected


Thank you so much; in advanced. I'm sure that these questions are so simple and I'm just missing something. I'm so sorry.

Tom

hi,
As you want to operate with low freq 10 thru 800Hz, use an input capacitor to suit.

What is the source of the input signal.?

 

[tom_pay]

Hi,

1) So the Bypass line needs a small capacitor (Say 5uF) to keep noise out of the power line. Like the capacitor usually put on the power lines on a PIC. Why isn't it just put there? On the power traces just before the IC?

2) For the coupling cap should I use the high pass filter formula?

3) Is this capacitor the AC Coupling capacitor.

I'm very sorry if I seem to be ignorant, but I'm really confused.

Thanks

Tom