Product Info

VTech proprietary and confidential
VTech Communications LTD.
R&D Department
The document is VTech’s proprietary information, Please do not disclose to third party without VTech’s consent
Ref. No.: 20191009 Version: 01 Date: 09 Oct, 2019 Page 14 of 33
• 16 kHz
• 22.050 kHz
• 24 kHz
• 32 kHz
• 44.1 kHz
• 48 kHz
7.2.2.2 ADC audio input gain
The VTBM-A01 BT Module audio input gain consists of the following components:
• An analog gain stage based on a pre-amplifier and an analog gain amplifier
• A digital gain stage
Figure 7-3 Audio input gain
7.2.2.3 ADC pre-amplifier and analog/digital gain
The gain of the ADC inputs can be configured in the range of -27 dB to 63.5 dB steps, making it suitable for
line and microphone input levels. 0 dB is 1600 mV pk-pk input.
The ADC input impedance is nominal 6 kΩ except when 0 dB pre-amplifier gain is selected when it becomes
12 kΩ.
If the input pre-amplifier is disabled, the input impedance varies between 6 kΩ and 34 kΩ, depending on gain
selection. In normal operation, the input pre-amplifier is enabled.
Calls connected by the VM stream automatically select the distribution of gain within the ADC for best
performance. Alternatively, the individual gain stages can be set.
7.2.2.4 ADC digital gain