Hello Duc,
The resistances used in your schematic do configure the OPA842 in an inverting configuration. The error seen in V_inv is mainly caused by the bias current of the device. With a typical bias current of 35uA, resistances of 402Ohms and an input…
Part Number: OPA842 The attached circuit has been verified on a ATE (VLCT) board. It was copied to a new ATE (V93K) board but is oscillating. Is there a spice model for this part so I can use Tina to run some simulation?
Thanks,
Cindy
Other Parts Discussed in Thread: OPA842 I am using the OPA842 in a traditional trans-impedance configuration with a BF862 as input buffer (included in the feedback-loop). Gain is 20dB up to around 10MHz.
I have measured IP3 on this amplifier with f1…
Hello,
I'm back to this topic, however i still don"t have any idea how to manage these requirements?
Has anyone have a good idea?
Thanks
Best regards,
MJ
I might want to increase the gain by an order of magnitude. Can you give me an accurate Cf calculation (formula) for 1pf and 10 meghahertz input signal? The Cf value is so low, that's why I want to use the alternative configuration. I will try to simulate…
did you try on real board ? well i am trying to use OPA842 now, what do you think of making two stages amplifier the first with unity gain stable opamp Opa842 and the second one with the opa847 ?
Thank you, i will be waiting for your test results.…
Me thinks the circuit from figure 48 is crap
I would do it this way:
https://e2e.ti.com/support/amplifiers/f/amplifiers-forum/763240/opa842-non-inverting-resistor-calculation
Kai
Your 1st circuit with the opamp circuit - that is positive feedback. Also, I am unclear how you expect the circuit to work.
Your 2nd circuit is open-loop...may not be the most optimum stable solution.
Here is a potential closed-loop opamp solution…
Hello Bivin,
For a range that large a log-amp (LOG112, LOG101) is the best solution. Unfortunately we do not have any high-speed log amps in our portfolio; they are mainly precision type amplifiers.
There are two choices -
1. Build a discrete amplifier…
