JAJSP64I December 2003 – October 2024 OPA695
PRODUCTION DATA
The design procedure begins with calculating the required signal gain and signal swing. After the gain and swing requirements are determined the appropriate amplifier is selected along with the required supply voltage. As a result of the input impedance of 50 Ω, the gain and the input impedance require a feedback resistor value of 400 Ω.
In this application, the supply voltage is 12 V and single ended. To provide the proper dc operating point, apply a midsupply voltage to the noninverting input by using a resistive voltage divider composed of two 1% precision 5-kΩ resistors along with two ceramic bypass capacitors. These components provide an accurate and low ac impedance reference voltage for the noninverting input. The inverting input requires only an ac-coupling capacitor to isolate the 6-V operating voltage from the signal source. In this example, a ceramic 1000-pF capacitor is used.
The circuit in Figure 7-10 shows an output resistor value of 50 Ω. Adjust this resistor to accommodate the SAW input impedance. Additional L/C components can be required as well; consult the SAW manufacturer's design guidelines for more details.