JAJSHP9E November 2007 – July 2019 VCA824
PRODUCTION DATA.
Because both inputs of the VCA824 are high-impedance, a difference amplifier can be implemented without any major problem. Figure 65 shows this implementation. This circuit provides excellent common-mode rejection ratio (CMRR) as long as the input is within the CMRR range of –2.1 V to 1.6 V. Note that this circuit does not make use of the gain control pin, VG. Also, it is recommended to choose RS such that the pole formed by RS and the parasitic input capacitance does not limit the bandwidth of the circuit. Figure 66 shows the common-mode rejection ratio for this circuit implemented in a gain of 10 V/V for VG = 1 V. Note that because the gain control voltage is fixed and is normally set to 1V, the feedback element can be reduced in order to increase the bandwidth. When reducing the feedback element, make sure that the VCA824 is not limited by common-mode input voltage, the current flowing through RG, or any other limitation described in this data sheet.