Opamp Example Project

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EfAv_4380776
Level 1
Level 1

Hello everyone.
I've been trying to implement a non-inverting amplifier for a couple of days without any success.

The kit I'm using is the PSoC 4200-BLE kit, CY8C4247LQ-BL483.

This is the example Opamp project I'm evaluating:

OpampPsoc.PNG

The input signal:

inputOpamp.PNG

The yellow is the input signal and the blue one the output.

opamp_osc.PNG

The thing is I've noticed the Vout hasn't the same frequency as the input signal. Furthermore, the oscilloscope can't even read it because it seems to change randomly.
This was the best result I could get and it was using 800mV sinewave as the Vin+. If I change this value, the Opamp doesn't amplify at all.

For example using 200mV as input:

200mV.PNG

Any ideas of why isn't it working properly?

I get that the Opamps inside the PSoC are single supplied so they can't amplify the negative side of the sine wave and the top of the output gets clipped because of the reference Voltage. Is it possible to change Vref from 3.3V to 5V internally so the Opamp can amplify up to 5V?

Thanks!

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MotooTanaka
Level 9
Level 9
Distributor - Marubun (Japan)
First comment on blog Beta tester First comment on KBA

Hi,

I tried this with CY8CKIT-044 (CY8C4247AZI-M485).

I noticed that there were a few points we can make mistakes

(1) Vout is needed to be an Analog Pin instead of a Digital Output Pin.

(2) Output of the Opamp must be "Output to pin."

(3) In the main.c, Opamp_Start() must be called.

IMG_4300.JPG

I copied your schematic

001-circuit.JPG

Vout

Note: Vout is not a Digital Output but another analog pin Flipped Horizontally

002-Vout.JPG

Vplus and Vminus

003-Vplus.JPG

004-Vminus.JPG

Opamp

005-OpAmp.JPG

Pins

006-pins.JPG

main.c

007-main_c.jpg

Oscilloscope waveforms

Note:

The upper RED signal is the source 0.8Vp-p 1kHz Sine Wave generated by FRDM-KL25Z.

The lower Yellow signal is the Vout

both has 0.5V unit.

IMG_4299.JPG

moto

P.S. I tried to intentionally made the mistakes above.

(1) and (2) could not be compiled.

(3) the result waveform looked like your waveform. (Output was flat)

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3 Replies
odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

efav,

You have ground loop so your 1kHz is floating against PSoC voltage at 50Hz. Thats why you see those splashes of outputs. You must connect the grounds of PSoC board and sine generator

Secondly, the sine generator provides +/- voltage centered around 0V, but the Opamp has reference voltage Vss=0, so only positive half of the Sine will be amplified. 

/odissey1

Hello BoTa, I've connected Oscilloscope Channel1(-), Channel2(-) and  Oscilloscope GND to the dev kit board's GND.
Still no success, now this is what I get:

new.PNG

new2.PNG

thanks!!

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lock attach
Attachments are accessible only for community members.
MotooTanaka
Level 9
Level 9
Distributor - Marubun (Japan)
First comment on blog Beta tester First comment on KBA

Hi,

I tried this with CY8CKIT-044 (CY8C4247AZI-M485).

I noticed that there were a few points we can make mistakes

(1) Vout is needed to be an Analog Pin instead of a Digital Output Pin.

(2) Output of the Opamp must be "Output to pin."

(3) In the main.c, Opamp_Start() must be called.

IMG_4300.JPG

I copied your schematic

001-circuit.JPG

Vout

Note: Vout is not a Digital Output but another analog pin Flipped Horizontally

002-Vout.JPG

Vplus and Vminus

003-Vplus.JPG

004-Vminus.JPG

Opamp

005-OpAmp.JPG

Pins

006-pins.JPG

main.c

007-main_c.jpg

Oscilloscope waveforms

Note:

The upper RED signal is the source 0.8Vp-p 1kHz Sine Wave generated by FRDM-KL25Z.

The lower Yellow signal is the Vout

both has 0.5V unit.

IMG_4299.JPG

moto

P.S. I tried to intentionally made the mistakes above.

(1) and (2) could not be compiled.

(3) the result waveform looked like your waveform. (Output was flat)