Constant-bandwidth-amplifier
The traditional restriction of constant gain-bandwidth 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 operational amplifier into a current amplifier. Feedback is then applied using resistors R2 and R1, transforming the entire circuit into a feedback voltage amplifier with a non-inverting gain (G) of 1 + R1/R2. Using the specified values, a constant bandwidth of 3.5 MHz is achieved for all voltage gains up to and beyond 100 at a 10 V peak-to-peak output, which corresponds to a gain-bandwidth product of 350 MHz from an operational amplifier with an advertised unity gain-bandwidth of 10 MHz. An inverting gain configuration is also feasible, represented as G ≈ R1/ZR2. Slewing rates are significantly enhanced with this method; even a 741 operational amplifier can handle 100 V/µs under these conditions since its output acts as a virtual earth. However, due to the new configurations utilizing current feedback to maintain bandwidth independence, an output buffer should be incorporated for applications requiring substantial output current.
The described circuit employs a feedback mechanism around a current amplifier to overcome the limitations of traditional voltage amplifiers regarding gain-bandwidth product. The use of two current mirrors, derived from transistors in a CA3096AE array, allows the LF351 operational amplifier to function as a current amplifier. This configuration is crucial in applications where high bandwidth and gain are necessary.
In this design, resistors R1 and R2 are integral to establishing the feedback loop, which defines the non-inverting gain of the amplifier. The gain formula, G = 1 + R1/R2, indicates that the gain can be adjusted by varying the resistor values, allowing for flexibility in circuit design. The achievement of a constant bandwidth of 3.5 MHz across gains exceeding 100 at a 10 V peak-to-peak output is notable, as it indicates a significant improvement in performance compared to standard operational amplifiers.
The gain-bandwidth product of 350 MHz is particularly impressive, given that the LF351 has a specified unity gain-bandwidth of 10 MHz. This enhancement is critical for high-frequency applications, where maintaining signal integrity is paramount. The alternative inverting configuration allows for further versatility, enabling the circuit to adapt to different signal processing requirements.
Slewing rates, which dictate how quickly an amplifier can respond to rapid changes in input signal, are improved significantly in this setup. The ability of a 741 operational amplifier to manage 100 V/µs under these conditions highlights the effectiveness of current feedback in enhancing performance. However, it is essential to incorporate an output buffer in designs where high output current is needed, as this ensures stable operation and prevents loading effects that could compromise the amplifier's performance. Overall, this circuit design represents a sophisticated approach to achieving high gain and bandwidth in voltage amplification applications.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. 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. 🔗 External reference
The described circuit employs a feedback mechanism around a current amplifier to overcome the limitations of traditional voltage amplifiers regarding gain-bandwidth product. The use of two current mirrors, derived from transistors in a CA3096AE array, allows the LF351 operational amplifier to function as a current amplifier. This configuration is crucial in applications where high bandwidth and gain are necessary.
In this design, resistors R1 and R2 are integral to establishing the feedback loop, which defines the non-inverting gain of the amplifier. The gain formula, G = 1 + R1/R2, indicates that the gain can be adjusted by varying the resistor values, allowing for flexibility in circuit design. The achievement of a constant bandwidth of 3.5 MHz across gains exceeding 100 at a 10 V peak-to-peak output is notable, as it indicates a significant improvement in performance compared to standard operational amplifiers.
The gain-bandwidth product of 350 MHz is particularly impressive, given that the LF351 has a specified unity gain-bandwidth of 10 MHz. This enhancement is critical for high-frequency applications, where maintaining signal integrity is paramount. The alternative inverting configuration allows for further versatility, enabling the circuit to adapt to different signal processing requirements.
Slewing rates, which dictate how quickly an amplifier can respond to rapid changes in input signal, are improved significantly in this setup. The ability of a 741 operational amplifier to manage 100 V/µs under these conditions highlights the effectiveness of current feedback in enhancing performance. However, it is essential to incorporate an output buffer in designs where high output current is needed, as this ensures stable operation and prevents loading effects that could compromise the amplifier's performance. Overall, this circuit design represents a sophisticated approach to achieving high gain and bandwidth in voltage amplification applications.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. 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. 🔗 External reference