- #1
chemnut220
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I have a temperature probe that I amplify with an OP amp and the circuit has to sit next to a video transmitter operating at 1280 MHz outputting ~ 800 mW of power.
I can get the circuit about a meter from the transmitter if I absolutely have to but it is going to be in somewhat close proximity.
I am not well versed in this sort of thing so my first design was with the good ol LM741. Well - the stupid thing worked really well and had no EMI problems (none that I could detect).
Then I wanted to operate on a single supply and a lower voltage (rail to rail) so I bought some TL972 opamps (was planning on using 2 stages on the same piece of IC - I can do that with a dual op amp right?).
Well I built a single stage inverting amp with a gain of 10 and it all looked nice until I turned the video transmitter on... not so good... the output voltage swung wildly all over the place. I tried adding capacitors between the in +, in - and virtual ground (everything I had in my box from 10pf to 1000 uf) which helped very little.
So I started reading about op amps and emi which brought me to stuff about EMIRR rating. I am about to order a few TLV2372 which have around -20db rejection in the band I am operating. That is actually kind of poor compared to some of the better EMI hardened opamps that TI has, but I need a pdip package so I can breadboard without strange modification to SMD packages (soldering jumper wires - i just can't bring myself to do it...) and the TLV2372 was the only one offered in this package with any sort of EMIRR rating (that I could find).
Does anybody have any suggestions? I want to operate on voltages between 6-8 (+/- 3-4) and would like to have pDIP packages if possible.
Thanks,
- Joe
I can get the circuit about a meter from the transmitter if I absolutely have to but it is going to be in somewhat close proximity.
I am not well versed in this sort of thing so my first design was with the good ol LM741. Well - the stupid thing worked really well and had no EMI problems (none that I could detect).
Then I wanted to operate on a single supply and a lower voltage (rail to rail) so I bought some TL972 opamps (was planning on using 2 stages on the same piece of IC - I can do that with a dual op amp right?).
Well I built a single stage inverting amp with a gain of 10 and it all looked nice until I turned the video transmitter on... not so good... the output voltage swung wildly all over the place. I tried adding capacitors between the in +, in - and virtual ground (everything I had in my box from 10pf to 1000 uf) which helped very little.
So I started reading about op amps and emi which brought me to stuff about EMIRR rating. I am about to order a few TLV2372 which have around -20db rejection in the band I am operating. That is actually kind of poor compared to some of the better EMI hardened opamps that TI has, but I need a pdip package so I can breadboard without strange modification to SMD packages (soldering jumper wires - i just can't bring myself to do it...) and the TLV2372 was the only one offered in this package with any sort of EMIRR rating (that I could find).
Does anybody have any suggestions? I want to operate on voltages between 6-8 (+/- 3-4) and would like to have pDIP packages if possible.
Thanks,
- Joe