Datasheet AD8010 (Analog Devices) - 10

AD8010 Differential Line Driver
In the circuit in Figure 31 the A device is configured as a gain- Twisted pair transmission lines are more often being used for of-two follower, while the B device is a gain-of-two inverter. high frequency analog and digital signals. Over long distances, These will produce a differential output signal whose maximum however, the attenuation characteristics of these lines can value is twice the peak-to-peak value of the maximum output degrade the performance of the transmission system. To com- of one device. For this circuit a 12 V peak-to-peak output can pensate for this, larger signals are transmitted, which after the be obtained. attenuation, will still have useful signal strength. The op amps drive a 1:2 step-up transformer that drives a The high output current of two AD8010s can be used along 100 Ω transmission line. Since the impedance reflected back to with a transformer to create a high power differential line driver. the primary varies as the square of the turns ratio, it will appear The differential configuration effectively doubles the output as 25 Ω at the primary. This source terminating resistor is split swing, while the step-up transformer further increases the out- as a 12.4 Ω resistor at the output of each device. put voltage. The circuit shown is capable of delivering 12 V p-p to the line and operates with a –3 dB bandwidth of 40 MHz. The peak current output of either op amp is 100 mA.
499 499 12.4 +6 AD8010 150 VIN 402 806 100 12.4 AD8010 –6 1:2 150
Figure 31. High Output Differential Line Driver Using Two AD8010s. NOTE: Please see Figure 29 for Recommended Bypassing Technique. –10– REV. B