JAJSHP9E November 2007 – July 2019 VCA824
PRODUCTION DATA.
This section describes the use of the VCA824 in a fixed-gain application in which the VG control pin is set at
VG = 1 V. The tradeoffs described here are with bandwidth, gain, and output voltage range.
In the case of an application that does not make use of the VGAIN, but requires some other characteristic of the VCA824, the RG resistor must be set such that the maximum current flowing through the resistance IRG is less than ±2.6 mA typical, or 5.2 mAPP as defined in Electrical Characteristics: VS = ±5 V, and must follow Equation 1.
As Equation 1 illustrates, once the output dynamic range and maximum gain are defined, the gain resistor is set. This gain setting in turn affects the bandwidth, because in order to achieve the gain (and with a set gain element), the feedback element of the output stage amplifier is set as well. Keeping in mind that the output amplifier of the VCA824 is a current-feedback amplifier, the larger the feedback element, the lower the bandwidth because the feedback resistor is the compensation element.
Limiting the discussion to the input voltage only and ignoring the output voltage and gain, Equation 2 illustrates the tradeoff between the input voltage and the current flowing through the gain resistor.