Monday , September 23 2019

Short Definition of Feed-Forward Compensation of Operational Amplifier

The TL080 through TL084 BIFET operational amplifiers have been developed by Texas Instruments through state-of-the-art semiconductor technology. The BIFET process allows optimum circuit design with the fabrication The TL080 through TL084 BIFET operational amplifiers have been developed by Texas Instruments through state-of-the-art semiconductor technology. The BIFET process allows optimum circuit design with the fabrication.

The TLOSO provides for externally controlled compensation on pins I and S. This is an advantage over the internally compensated version (TLOSI) because it allows the user to obtain slew rates from a typical 12 V/uS (for nominal compensation of 12 pF) to 30 V/uS (for a compensation of 3 pF). This increased slew rate is also reflected in the small signal response where the rise time is decreased from 0.1 uS to less than 50 ns. The power bandwidth can be extended to greater than 1 MHz. This greatly increases the potential for large-signal wide-bandwidth applications and for filters with frequencies at or above 1 MHz. The unity gain bandwidth is identical to the normal compensation mode but the first pole frequency is extended above 10 kHz; thus, gain accuracy is maintained at higher frequencies.

In the feed-forward circuit (see Figure 2-13), a 100 kOhm resistor is shown in parallel with a 3 pF capacitor in the negative feedback loop. A 500 pF feed-forward capacitor is connected from pin I to the inverting input of the TLOSO. The high-frequency response increases from approximately 6 kHz to over 200 kHz. Figure 2-14 is the feed-forward compensation curves.

Figure 2-13. Feed-Forward Compensation

OPEN·LOOP LARGE SIGNAL
DIFFERENTIAL VOLTAGE GAIN
vs
FREQUENCY

Figure 2-14. Feed-Forward Compensation Curves

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