INTEGRATED VARIABLE GAIN AMPLIFIERS

摘要

Aline of variable gain amplifiers (VGA) has been introduced for use in transmitter and receiver automatic gain control (AGC) circuits, and as variable gain blocks following low noise amplifier stages in high dynamic range receiver front ends. The new amplifiers integrate high performance amplifiers and attenuators within a single surface-mount package optimized for wireless infrastructure and other telecommunications applications. The new amplifier series consists of the models VG101 and VG111 integrated VGAs that maintain constant intercept and compression point performance over the entire gain control range. Both amplifiers feature a wide dynamic range of over 30 dB and a 4.3 or better noise figure (NF) at maximum gain. They operate from a single positive bias supply and are matched to 50 Ω over the full attenuation range to ensure proper operation when cascaded with other RF elements such as filters. The combination of gain, NF, attenuation and third-order intercept (IP3) make these devices ideal for base station transmitter and receiver chains that process complex digital modulation formats such as CDMA, GSM, PCS and UMTS. The amplifiers are also well suited for cable, ISM, WLL, WLAN and defense applications. The model VG024 VGA is well suited for temperature compensation circuits with independent gain and slope adjustment. Table 1 lists the key specifications of each of the three models.