Posted on Jan 9, 2013

The traditional restnct1on of constant gainbandwidth products for a voltage amplifier can be overcome by employing feedback around a current amplifier. Two current mirrors, constructed from transistors in a CA3096AE array, effectively turn the LF351 op amp into a current amplifier. Feedback is then applied by using R2 and R1, turning the whole circuit into a feedback voltage amplifier with a noninverting gain of G of 1 + R112R2.

Click here to download the full size of the above Circuit.

Using the values shown, a constant bandwidth of 3.5 MHz is obtained for all voltage gains up to and beyond 100 at 10 V pk-pk output, equivalent to a gain-bandwidth product of 350 MHz from an op amp with an advertised unity gain-bandwidth of 10 MHz. An inverting gain configuration is also possible (see Fig. 2) where G ~ R1/ZR2. Slewing rates are significantly improved by this approach; even a 741 can manage 100 V p,s under these conditions since its output is a virtual earth. However, because the new configurations use current feedback to achieve bandwidth independence, an output buffer should be added for circuits where a significant output current is required.

Leave Comment

characters left:

New Circuits



Popular Circuits

Temperature Controller With Defrost Cycle
Stablised Power Supply With Short Circuit Indication
driving stepper motor using uln2003
15w rf amplifier circuit
Lets to build many VU Meter circuits with LM3914
modifying fm transmitter circuit 3
designing audio circuit tape delay
A Cmos Based Motorcycle Alarm circuit
5000 watts power inverter
1-20 minutes a timing circuit
Lantern making use of a relay control circuit