AD744Table II. Recommended Values of CCOMP vs. Various Load Conditions for the Circuits of Figures 31 and 32.MaxSlew–3 dBR1R2GainGainCLOADCCOMPCLEADRateBandwidth( ⍀ )( ⍀ )FollowerInverter(pF)(pF)(pF)(V/ s)(MHz) 4.99 k 4.99 k 2 1 50 0 7 75 2.51 4.99 k 4.99 k 2 1 150 5 7 37 2.31 4.99 k 4.99 k 2 1 1000 20 – 14 1.2 4.99 k 4.99 k 2 1 >2000 25 – 12.52 1.0 499 Ω 4.99 k 11 10 270 0 – 75 1.2 499 Ω 4.99 k 11 10 390 2 – 50 0.85 499 Ω 4.99 k 11 10 1000 5 – 372 0.60 NOTES 1Bandwidth with CLEAD adjusted for minimum settling time. 2Into large capacitive loads the AD744’s 25 mA output current limit sets the slew rate of the amplifier, in V/ µs, equal to 0.025 amps divided by the value of CLOAD in µF. Slew rate is specified into rated max CLOAD except for cases marked 2, which are specified with a 50 pF. load. CLEAD* Due to manufacturing variations in the value of the internal R2* CCOMP, it is recommended that the amplifier’s response be +V optimized for the desired gain by using a 2 to 10 pF trimmer S capacitor rather than using a fixed value. 1 F0.1 FR1*VINR1*R2*AD744VOUT+VSOPTIONAL1 F0.1 FCCOMP1 F0.1 FAD744VOUT*SEE TABLE II–VSNOT CONNECTED \ VIN Figure 32. AD744 Connected as an Inverting Amplifier 2 – 10pF Operating at Gains of 1 or Greater *SEE TABLE III1 F0.1 F–VSUsing Decompensation to Extend the Gain Bandwidth Product Figure 33. Using the Decompensation Connection to When the AD744 is used in applications where the closed-loop Extend Gain Bandwidth gain is greater than 10, gain bandwidth product may be enhanced by connecting a small capacitor between Pins 1 and 5 (Figure 33). At low frequencies, this capacitor cancels the effects of the Table III. Performance Summary for the Circuit of Figure 33 chip’s internal compensation capacitor, CCOMP, effectively dec- R1R2GainGain–3 dBGain/BW ompensating the amplifier. ( ⍀ )( ⍀ )FollowerInverterBandwidthProduct 1 k 10 k 11 10 2.5 MHz 25 MHz 100 10 k 101 100 760 kHz 76 MHz 100 100 k 1001 1000 225 kHz 225 MHz REV. C –9–