ADPA1107

• Complete Bias Control and Sequencing Solution for Pulsed GaN Radar Power Amplifiers
• Pin Compatible with ADI's existing Pulser Board and with ADI's GaN Power Amplifier Evaluation Boards
• Operation in Drain Pulsed Mode or Gate Pulsed Mode
• Optional Crowbar Circuit for Fast Turn Off in Drain Pulsed Mode
• Single 24 V to 50 V Power Supply with on-board Negative Gate Voltage Generation.
• Drain Current Monitoring Circuit

Pulser Plus is a reference design for biasing Gallium Nitride RF Power Amplifiers. It plugs directly into Analog Devices’ GaN PA evaluation boards such as ADPA1106 and ADPA1107. The only input signals required to control and operate the board are a power supply voltage between 24 V and 50V and a 0V/3V signal on the Drain Pulse Enable or Gate Pulse Enable digital inputs.

Pulser Plus was specifically designed to enable fast pulsing of GaN Radar Power Amplifiers. It can support RF pulses as short as 1us and with rise and fall times of less than 100 ns in both Drain Pulsed mode and Gate Pulsed Mode.

The ADPA1107-EVALZ consists of a 2-layer printed circuit board (PCB) fabricated from a 10 mil thick, Rogers 4350B copper clad mounted to an aluminum heat spreader. The heat spreader assists in providing thermal relief to the device as well as mechanical support to the PCB. Mounting holes on the heat spreader allow the spreader to be attached to a heat sink. Alternatively, the spreader can be clamped to a hot and cold plate. The RFIN and RFOUT ports on the ADPA1107-EVALZ are populated by 2.92 mm (K) female coaxial connectors, and the respective RF traces have a 50 Ω characteristic impedance. The ADPA1107-EVALZ is populated with components suitable for use over the entire operating temperature range of the device. To calibrate board trace losses, a through calibration path is provided between the J6 and J5 connectors. J6 and J5 must be populated with 2.92 mm (K) female coaxial connectors to use the through calibration path.

The ground, power, gate control, and detector output voltage are provided through two test points (TP1 and TP2) and two 24-pin headers (J3 and J4) on the ADPA1107-EVALZ. The pinouts for these four headers are detailed in Table 1.

RF traces on the ADPA1107-EVALZ are 50 Ω, grounded, coplanar waveguide. The package ground leads and the exposed pad connect directly to the ground plane. Multiple vias connect the top and bottom ground planes with particular focus on the area directly beneath the ground pad to provide adequate electrical conduction and thermal conduction to the heat spreader.

The ADPA1107-EVALZ ships with a drain pulsing board (pulser board) that can be plugged into the ADPA1107-EVALZ headers and configured to control the biasing of the ADPA1107 by providing a negative gate voltage and a control signal that connects and disconnects the drain voltage to the ADPA1107-EVALZ. The ADPA1107-EVALZ can also operate alone in gate pulsed mode where a negative pulse is applied to the VGG1 pin of the ADPA1107.

For full details on the ADPA1107, see the ADPA1107 data sheet, which must be consulted in conjunction with the user guide when using the ADPA1107-EVALZ.