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Topic: Ne5534 OPAMP amplifier (Read 3108 times) previous topic - next topic

shivakumarj1995

I came up with the following circuit for amplifying the output AC sinusiodal signal of the CT. Which has a peak voltage of 15mv 50hz sinewave. Now when I connected the circuit and powered it with 5v I measured the output using a multimeter and I saw that the output was 5v. And when I connected the signal from the CT. Nothing changed. The value remained the same. What is wrong with this?. Could someone please suggest anything?

Jiggy-Ninja

#1
Feb 21, 2017, 05:13 pm Last Edit: Feb 21, 2017, 05:14 pm by Jiggy-Ninja
What's that chopped off on the right-hand side? Do you have the output connected to 5V?


shivakumarj1995

That is connected to the ADC of a microcontroller. The output is not connected to 5v.  :)

shivakumarj1995

Could the fact that ne5534 is an audio amplifier be a source of the problem?

Jiggy-Ninja

#4
Feb 21, 2017, 05:55 pm Last Edit: Feb 21, 2017, 05:56 pm by Jiggy-Ninja

Grumpy_Mike

#5
Feb 21, 2017, 06:03 pm Last Edit: Feb 21, 2017, 06:05 pm by Grumpy_Mike
Could the fact that ne5534 is an audio amplifier be a source of the problem?
Well you are not powering it correctly. The data sheet says:-
Quote
Wide Supply-Voltage Range ±3 V to ±20 V
So that means that 6V is the lowest voltage that it takes to drive correctly and you only have 5V.

The Recommended Operating Conditions is a minimum of +5V and -5V, so you are way off that.

polymorph

1M/20k = 50

But at higher gain, that configuration is going to become unstable. An attenuator would be better than that particular way of varying the gain.

If you need voltage gain in the range of 100x, it is better to distribute the gain between two Op Amps.

Also, the NE5534 is rated for a minimum of +-3V, at least the On Semiconductor version is. Other manufacturers may have other ratings.
Steve Greenfield AE7HD
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Grumpy_Mike

#7
Feb 21, 2017, 08:35 pm Last Edit: Feb 21, 2017, 08:35 pm by Grumpy_Mike
Quote
Also, the NE5534 is rated for a minimum of +-3V, at least the On Semiconductor version is.
Yes it says that in the "headline" but it also says:-

polymorph

The On Semi version says:

Quote
Large Supply Voltage Range: +-3.0 to +-20 V
I didn't look at datasheets for any other manufacturers for this. I did say they may be different.

http://www.onsemi.com/pub_link/Collateral/NE5534-D.PDF

It also says 10Vrms with +-18V supplies, which is going to be only 14Vpk. Leaving very little overhead if running this from merely +-5V supplies.

I'm trying to say that this is a bad choice for this purpose.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

Grumpy_Mike

Quote
Leaving very little overhead if running this from merely +-5V supplies.
Yes but he is not using +-5V, just a single ended 5V so that corresponds to +-2.5V. So he is trying to operate it out of spec.

That bit I posted was from the Ti data sheet.

MarkT

Use a rail-to-rail opamp from 5V.  How are you connecting the current transformer (that circuit appears to be
a slice of a diagram for an electret condenser microphone amplifier).

Does your CT have a built-in burden resistor?  What value is it?  You'll need to not load down that
burden resistor load significantly or you'll change the output level.  Use a non-inverting opamp
circuit to avoid loading the source perhaps?
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

shivakumarj1995

#11
Feb 22, 2017, 02:12 am Last Edit: Feb 22, 2017, 02:35 am by shivakumarj1995
Use a rail-to-rail opamp from 5V.  How are you connecting the current transformer (that circuit appears to be
a slice of a diagram for an electret condenser microphone amplifier).

Does your CT have a built-in burden resistor?  What value is it?  You'll need to not load down that
burden resistor load significantly or you'll change the output level.  Use a non-inverting opamp
circuit to avoid loading the source perhaps?
There is a burden resistor of 200ohm parallel to the CT. So you are saying in should use connect the CT output into the non inverting input of the OPAMP? I don't have access to - + dual supplies only a few adaptors. So I will power it with 12v supply and see what it does.

shivakumarj1995

Well you are not powering it correctly. The data sheet says:-So that means that 6V is the lowest voltage that it takes to drive correctly and you only have 5V.

The Recommended Operating Conditions is a minimum of +5V and -5V, so you are way off that.
I don't have access to a dual supply only a few adapters. So I will power it through a 12 V or 9v supply and see what it does.

Grumpy_Mike

It will blow up your Arduino because the output will be over 5V. It needs to be reduced with a potential divider before feeding it into the Arduino.

Why not just get a decent op-amp?

shivakumarj1995

It will blow up your Arduino because the output will be over 5V. It needs to be reduced with a potential divider before feeding it into the Arduino.

Why not just get a decent op-amp?
Of course I won't be giving any signal more than 5v to the arduino I wanted to atleast amplify the 15mv signal using the OPAMP. I put a 12v supply and the output still is going all the way to the 12v even without any input signal

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