Wideband, Low Power, Variable Gain Amplifier

The LMH6504 is a wideband DC coupled voltage controlled gain stage followed by a high-speed current feedback Op Amp which can directly drive a low impedance load. Gain adjustment range is 80 dB for up to 10 MHz by varying the gain control input voltage, VG.

Maximum gain is set by external components, and the gain can be reduced all the way to cut-off. Power consumption is 110 mW with a speed of 150 MHz and a gain control bandwidth (BW) of 150 MHz. Output referred DC offset voltage is less than 55 mV over the entire gain control voltage range. Device-to-device gain matching is within ±0.42 dB at maximum gain. Furthermore, gain is tested over a wide range. The output current feedback Op Amp allows high frequency large signals (Slew Rate > 1500 V/μs) and can also drive a heavy load current (60 mA). Near ideal input characteristics (i.e. low input bias current, low offset, low pin 3 resistance) enable the device to be easily configured as an inverting amplifier as well (see Application Information section for details).

To provide ease of use when working with a single supply, VG range is set to be from 0V to +2V relative to the ground pin potential (pin 4). VG input impedance is high in order to ease drive requirement. In single supply operation, the ground pin is tied to a "virtual" half supply.

LMH6504 gain control is linear in dB for a large portion of the total gain control range. This makes the device suitable for AGC applications. For linear gain control applications, see the LMH6503 data sheet.

The combination of minimal external components and small outline packages (SOIC and VSSOP) allows the LMH6504 to be used in space-constrained applications.