Gain block amplifier uses SiGe bipolar technology

Offering linearity of 47dBm OIP3 (output third order intercept) and 3.22dB noise figure at 150MHz, the LTC6433-15 is a wideband 15dB gain block amplifier from Linear Technology.

It has OP1dB (output 1dB compression point) of 19.2dBm. Its core is built using high frequency SiGe bipolar technology, distinguishing it 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 to 30MHz, so are prone to high noise floor rise, which renders them unusable at low frequencies, says the company. The high frequency SiGe bipolar technology enables the amplifier to exhibit lower 1/f noise corner, typically below 10kHz, making it usable at low frequencies to 100kHz without significant noise rise. Moreover, the performance of GaAs and pHEMT type devices depends on internal FET bias voltage, which can vary widely from part to part, according to the company, whereas the LTC6433-15 performance is stable over temperature and from device to device, and is insensitive to power supply voltage variations.

The low frequency capability broadens its use and improves performance in a wide range of amplifier applications, including cable networks, broadband signal sources, radar receiver IF amplifiers, VHF/UHF broadcast radios and RF test instrumentation. It offers an alternative to op amps in amplifier applications that do not require DC coupling.

The input and output are 50Ohm wideband matched from 100kHz to 1GHz with 1dB flatness over that frequency range. It has a -3dB bandwidth of 1.4GHz. 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. The amplifier simplifies wideband design and allows cascading with minimal external components. The DC2168A evaluation circuit covers the 100kHz to 1GHz band with flat gain, low noise and industry leading distortion performance.

The device operates from a single 5V supply and draws a nominal 95mA supply current. It is specified for operation over a case temperature range of   ̶-40 to +85°C and is available in a 4.0 x 4.0mm plastic QFN package.


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