LT1228 Datasheet PDF

●The LT1228CS8#PBF is a 100MHz current Feedback Amplifier with DC gain control. The LT1228 makes it easy to electronically control the gain of signals from DC to video frequencies. The LT1228 implements gain control with a transconductance amplifier (voltage to current) whose gain is proportional to an externally controlled current. A resistor is typically used to convert the output current to a voltage, which is then amplified with a current feedback amplifier. A complete differential input, gain controlled amplifier can be implemented with LT1228 and just a few resistors. The LT1228 transconductance amplifier has a high impedance differential input and a current source output with wide output voltage compliance. The transconductance, gm is set by the current that flows into Pin 5, ISET. The small signal gm is equal to ten times the value of ISET and this relationship holds over several decades of set current. The voltage at Pin 5 is two diode drops above the negative supply, Pin 4.

● Very fast transconductance amplifier

● Outputs swing within 0.8V of supplies

● gm = 10 x ISET

● Low THD (0.2% at 30mVRMS input)

● Wide ISET range (1µA to 1mA)

● Very fast current feedback amplifier bandwidth (100MHz)

● 0.04% Differential gain

● 0.1° Differential phase

● High input impedance (25MR, 6pF)

● Wide supply range (±2 to ±15V)

● Inputs common mode to within 1.5V of supplies

● 7mA Supply current