LT6402-12 BLOCK DIAGRAM 200Ω VEEA –INA VCCA 100 14pF Ω 14 – +OUT A 5 –INB 100Ω +OUTFILTERED 13 + 50Ω 6 VEEA 200Ω VCCC VOCM + 2 C 14pF – VEEC 200Ω 50Ω –OUTFILTERED +INA VCCB 100Ω 7 16 + –OUT B 8 +INB 100Ω 15 – 14pF VEEB VEEB 200Ω BIAS 64026 BD 3 10 1 11 4 9 12 VCCA VCCB VCCC ENABLE V V V EEA EEB EEC APPLICATIONS INFORMATIONCircuit Description Referring to the block diagram, the LT6402-12 uses a closed-loop topology which incorporates 3 internal am- The LT6402-12 is a low noise, low distortion differential plifi ers. Two of the amplifi ers (A and B) are identical and amplifi er/ADC driver with: drive the differential outputs. The third amplifi er is used • –3dB bandwidth to set the output common mode voltage. Gain and input DC to 300MHz impedance are set by the 200Ω resistors in the internal • Fixed gain independent of R feedback network. Output impedance is low, determined LOAD 4V/V (12dB) by the inherent output impedance of amplifi ers A and B, and further reduced by internal feedback. • Differential input impedance 100Ω The LT6402-12 also includes built-in single-pole output fi ltering. The user has the choice of using the unfi ltered • Low output impedance outputs, the fi ltered outputs (75MHz –3dB lowpass), or • Built-in, user adjustable output fi ltering modifying the fi ltered outputs to alter frequency response by adding additional components. Many lowpass and • Requires minimal support circuitry bandpass fi lters are easily implemented with just one or two additional components. 640212fa 10
