The power consumption requirements for digital cellular handsets differ dramatically from those for analog handsets. The ?bursty? nature of the transmission places rapidly varying transient current requirements on the handset's battery. Simulating the battery's performance accurately during production testing requires a power supply with a wide bandwidth (to minimize voltage drop at the phones during large current transients) as well as circuitry capable of emulating the impedance of the battery. To achieve maximum performance, the impedance of the load, which includes the DUT, cables, and fixturing, must also be kept to a minimum. Voltage and current stability, including freedom from oscillation, overshoot, undershoot, etc., are essential to achieve accurate test results. White Paper #2209