15dB high-linearity gain block: 47 dBm, 100 kHz to 1.4 GHz

July 22, 2016 // By Graham Prophet
LTC6433-15 is a wideband 15 dB gain block amplifier offering linearity of 47 dBm OIP3 (output third order intercept) and 3.22 dB noise figure at 150 MHz. The amplifier has OP1dB (output 1 dB compression point) of 19.2 dBm.

The LTC6433-15 is, Linear Technology asserts, different from other gain block amplifiers that are typically built using GaAs or pHEMT processes. These FET technologies have high 1/f noise corners on the order of 20 MHz to 30 MHz, so are prone to high noise floor rise, which renders them unusable at low frequencies. The LTC6433-15 amplifier core is built using high frequency SiGe (silicon-germanium) bipolar technology. As a result, the amplifier exhibits much lower 1/f noise corner, typically below 10 kHz, making it usable at low frequencies to 100 kHz without significant noise rise. Moreover, the performance of GaAs and pHEMT type devices is highly dependent on their internal FET bias voltage, which can vary widely from part to part. LTC6433-15 is stable over temperature and from device to device, and is insensitive to power supply voltage variations.

 

This low frequency capability is applicable to cable networks, broadband signal sources, radar receiver IF amplifiers, VHF/UHF broadcast radios and RF test instrumentation. The LTC6433-15 offers a superior alternative to many op amp solutions in amplifier applications that do not require DC coupling.

 

The LTC6433-15 input and output are 50Ω wideband matched from 100 kHz to 1 GHz with 1 dB flatness over that frequency range. It has a –3 dB bandwidth of 1.4 GHz. The amplifier needs only an input and output DC blocking capacitor, plus a choke to bias its open collector output, and one feedback capacitor to set the matching and gain flatness at low frequencies. It simplifies wideband design and allows easy cascading with minimal external components. The DC2168A evaluation circuit demonstrates this performance, covering the 100 kHz to 1 GHz band with flat gain, low noise and low distortion.

 

The LTC6433-15 operates from a single 5V supply. It draws a nominal 95mA supply current. The device is specified for operation over a case temperature range of –40°C to 85°C. The amplifier is available in