The LMH6515 is a high performance, digitally controlled variable gain amplifier (DVGA).
It combines precision gain control with a low noise, ultra-linear, differential amplifier.
Typically, the LMH6515 drives a high performance ADC in a broad range of mixed signal and digital
communication applications such as mobile radio and cellular base stations where automatic gain
control (AGC) is required to increase system dynamic range. When used in conjunction with a high
speed ADC, system dynamic range can be extended by up to 32 dB.
The LMH6515 has a differential input and output allowing large signal swings on a single
5V supply. It is designed to accept signals from RF elements and maintain a terminated impedance
environment. The input impedance is 200Ω resistive. The output impedance is either 200Ω or 400Ω and
is user selectable. A unique internal architecture allows use with both single ended and
differential input signals.
Input signals to the LMH6515 are scaled by a highly linear, digitally controlled
attenuator with 31 accurate 1 dB steps. The attenuator output provides the input signal for a high
gain, ultra linear differential transconductor. The transconductor differential output current can
be converted into a voltage by using the on-chip 200Ω or 400Ω loads. The transconductance gain is
0.1 Amp/Volt resulting in a maximum voltage gain of +26 dB when driving a 200Ω load, or 32 dB when
driving the 400Ω load. On chip digital latches are provided for local storage of the gain setting.
The gain step settling time is 5 ns and care has been taken to reduce the sensitivity of bandwidth
and phase to gain setting.
The LMH6515 operates over the industrial temperature range of −40°C to +85°C. The LMH6515
is available in a 16-Pin, thermally enhanced, WQFN package.
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