OPA656 is a broadband, unity gain stable, field-effect transistor input operational amplifier 14

d) The connection with other broadband devices on the board can be achieved through short direct tracking or through vehicle transmission lines. For short connections, consider tracking and the input of the next device as a lumped capacitive load. Relatively wide traces (50mils to 100mils) should be used, diodepreferably with the ground and power plane open around. Estimate the total capacitance load and set RS from the graph of recommended RS and capacitance load. Low parasitic capacitance load (<5pF) may not require RS, as OPA656 is nominally compensated to operate with 2pF parasitic load. If long tracking is required, higher parasitic capacitance loads without RS are allowed with increased signal gain (increasing no-load phase margin), and the inherent 6dB signal loss of the double ended transmission line is acceptable. diode Use microstrip or strip line technology to achieve matched impedance transmission lines (please refer to the ECL Microstrip and Strip Line Layout Technology Design Manual). Usually, a 50 ohm environment is not required on board, in fact, a high impedance environment will improve distortion, as shown in the distortion and load diagram. Based on the characteristic board tracking impedance defined by the sheet metal and tracking dimensions, use a matching series resistor that enters tracking from the output of OPA656 and a parallel resistor connected to the input terminal of the destination device. At the same time, the terminating impedance will be a parallel combination of the parallel resistor and the input impedance of the target device - this total effective impedance should be set to match the tracking impedance. If the 6dB attenuation of the dual ended transmission line is unacceptable, long tracking can only be terminated in series at the source end. In this case, consider tracking as a capacitive load and set the series resistance value as shown in the diagram of RS and capacitive load. This will not maintain signal integrity and double ended wiring. If the input impedance of the target device is low, the voltage divider formed by the series output will cause signal attenuation and enter the terminal impedance.diode

e) It is not recommended to insert high-speed components such as OPA656. The additional lead length introduced by the socket and the capacitance for the pins can create an extremely troublesome parasitic network, which is almost impossible to achieve a smooth and stable frequency response. Welding OPA656 onto the board can achieve the best results. diode

Input and ESD protection

OPA656 is built on a very high-speed complementary bipolar process. For these very small geometric devices, the internal junction breakdown voltage is relatively low. These subdivisions are reflected in the absolute maximum rating table. As shown in Figure 5, all device pins are protected by internal ESD protection diodes for power supply. diode

These diodes provide moderate protection against input overvoltage higher than the power supply. Protective diodes typically support a continuous current of 30mA. If there is a possibility of higher current (for example, in a system with ± 12V power supply components driven to OPA656), current limiting series resistors should be added at both input terminals. Keep these resistance values as low as possible, as high values can reduce noise performance and frequency response. diode