JAJSHP9E November 2007 – July 2019 VCA824
PRODUCTION DATA.
The VCA824 has a input dynamic range limited to 1.6 V and –2.1 V. Increasing the input voltage dynamic range can be done by using an attenuator network on the input. If the VCA824 is trying to regulate the amplitude at the output, such as in an AGC application, the input voltage dynamic range is directly proportional to Equation 2.
As such, for unity-gain or under-attenuated conditions, the input voltage must be limited to the CMIR of ±1.6 V (3.2 VPP) and the current (IRQ) must flow through the gain resistor, ±2.6 mA (5.2 mAPP). This configuration sets a minimum value for RE such that the gain resistor must be greater than Equation 3.
Values lower than 615.4 Ω are gain elements that result in reduced input range, as the dynamic input range is limited by the current flowing through the gain resistor RG (IRG). If the IRG current limits the performance of the circuit, the input stage of the VCA824 goes into overdrive, resulting in limited output voltage range. Such IRG-limited overdrive conditions are shown in Figure 40 for the gain of 10V/V and Figure 60 for the gain of 40 V/V.