PSoC5LP Op amp output current

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SaKu_291986
Level 4
Level 4
10 replies posted 10 questions asked 5 solutions authored

I have an op amp component buffering an internal 1.024V reference. I have connected a 1.2kΩ on the output. The voltage I get is 700mV instead of 1024mV. I need to source and sink 20mA from this pin. How can I do it?

Kumar

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1 Solution
odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

SaKu,

Please make sure that you connected resistor to the Opamp direct output pin (P3_6, P3_7, P0_0, P0_1). Direct pins have low resistance, while other pins may have 250-500 oHm resistance path from Opamap to the resistor. So the resulting voltage will be something like V = 1.024V x 1200 / (500 + 1200) = 0.723 V.

Keep in mind that even direct connection has some resistance, and Opamaps have some bias offset, so the output voltage will not be exact 1.024V.

You can find discussion of the same issue here:

Re: How to outputting internal 1.024V Vref inPSoC 5LP

/odissey1

KIT-059 annotation component: KIT-059: annotation component for CY8CKIT-059 PSoC5LP Prototyping Kit

KIT-059_06_B.png

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3 Replies
LinglingG_46
Moderator
Moderator
Moderator
500 solutions authored 1000 replies posted 10 questions asked

1: If you configure the Opamp as a follower, the internal 1.024 which be output should also be 1.024v.

2: connect the resistor: 1024mv/20mA

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

SaKu,

Please make sure that you connected resistor to the Opamp direct output pin (P3_6, P3_7, P0_0, P0_1). Direct pins have low resistance, while other pins may have 250-500 oHm resistance path from Opamap to the resistor. So the resulting voltage will be something like V = 1.024V x 1200 / (500 + 1200) = 0.723 V.

Keep in mind that even direct connection has some resistance, and Opamaps have some bias offset, so the output voltage will not be exact 1.024V.

You can find discussion of the same issue here:

Re: How to outputting internal 1.024V Vref inPSoC 5LP

/odissey1

KIT-059 annotation component: KIT-059: annotation component for CY8CKIT-059 PSoC5LP Prototyping Kit

KIT-059_06_B.png

Thank you very much odissey1. My problem is solved.

Kumar

0 Likes