Hello
What's the of op amp gbwp and whats the meaning of higher and lower bandwidth?
Excuse me for elementary questions
If the GBWP ( Gain Bandwidth Product ) of an operational amplifier is 1 MHz, it means that the gain of the device falls to unity at 1 MHz. Hence, when the device is wired for unity gain, it will work up to 1 MHz (GBWP = gain × bandwidth, therefore if BW = 1 MHz, then gain = 1) without excessively distorting the signal.
Bandwidth is the frequency range. High means a large range of frequency lower means less. When the gain falls below one it is no longer able to amplify.
And all opamps have a gain that falls off with frequency such that the product of gain and bandwidth is
basically constant from a few tens of Hz upto MHz (if the device goes that high). This is a consequence
of the amplifier having to be stable in a closed-loop feedback setup.
If you want accurate low distortion behaviour from an opamp you want to stay well below the
gain-bw product.
This is one of the reasons its recommended to limit each opamp to a low gain of 10 to 20 and
string several together for higher gain. A single stage with gain 1000x has about 100 less bandwidth
than 3 linked 10x stages (this can be a show-stopper if you're not expecting it!)
The exception to this is instrumentation amplifiers (like strain-guage and thermocouple amps) where single
stages with high gain are common - but the bandwidth requirements are very modest.
For audio use you'd want a bandwidth of 20kHz typically, meaning a gain-bw product of several MHz is
needed. For an opamp before an ADC sampling at 1kSPS, a lower gain-bw product of 100kHz would
likely be enough.
Another specification useful for bandwidth calculations is the output slew-rate, this limits the dV/dt
at the output, and affects gain at high output amplitude independently of the gain-bw product.