Compensation for op amp TLC07x

Hi Majo,

The TLC072 and other amplifiers in the family have a gain bandwidth (GBW) of 10 MHz. That is the frequency where the open-loop gain passes through 1 V/V (0 dB) and is decreasing as the frequency is increased. Realistically, the GBW of the TLC07x is too low to be used for a 10 MHz application of any sort. Also, the amplifier has to have sufficient slew rate to prevent slew rate limiting the input signal. The minimum slew rate is determined by how wide and fast the output signal must swing.

You will need an operational amplifier have much higher GBW such that there is reasonably high open-loop gain at 10 MHz. Even our fastest precision operational amplifier, the OPA354 which has a GBW of 250 MHz. has only 20 dB (10 V/V) of open-loop gain remaining at 10 MHz. You'll likely need at least 40 dB of open-loop gain at 10 MHz to get reasonably accurate circuit performance at that frequency. This places your application in the realm of needing a fast, wideband operational amplifier.

Nearly all operational amplifiers are internally compensated and a simple current source, driving a resistive load, will not likely require any additional compensation. If the load has a capacitive component, the external compensation may be required to keep the amplifier stable.

I suggest you post your inquiry again, but to the E2E High-Speed Amplifiers forum. They have numerous operational amplifiers with GBW ratings in the hundreds of Megahertz and Gigahertz. With the right amplifier you should be able to devise a good, accurate 10 MHz ac current source.

Regards, Thomas

PA -Linear Applications Engineering