The LMH6514 is a high performance, digitally controlled variable gain amplifier (DVGA). It combines precision gain control with a low noise, ultra-linear, differential amplifier. The LMH6514 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 auto- matic gain control (AGC) is required to increase system dy- namic range. When used in conjunction with a high speed ADC, system dynamic range can be extended by up to 42 dB. The LMH6514 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 re- sistive. 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 LMH6514 are scaled by a highly linear, digitally controlled attenuator with seven accurate 6 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 +32 dB when driving a 200
