Cell-phone downconverter packs dual mixers, low-noise amp

-- EDN, 4/13/2000

For use in dual-band cell phones that support both Global System for Mobile communications (GSM) and time-division multiple-access (TDMA) modes, the Motorola MC13740A IC incorporates two complete downconverters in one package. Each downconverter provides a low-noise, variable-gain amplifier, a local-oscillator output and a mixer for frequencies as high as 2 GHz. Input third-order-intercept point for each mixer is 10 dBm at 850 MHz, and you can improve this figure to 15 dBm via an external adjustment. Mixer and local-oscillator inputs are single-ended, and the double-balanced mixer output has a differential, open-collector topology. The 2.75V, 24-pin surface-mount device (picture) also includes a metal contact on its backside, which gives you a low-inductance RF path to pc-board ground. The MC13740A sells for $3 (10,000).

Motorola Semiconductor, www.motorola.com/wireless-semi/.

-by Bill Schweber