DC550A Analog Devices

May 12, 2004 Demo Circuit DC550A Quick Start Guide. Introduction Demo circuit DC550A demonstrates operation of the LT5514 IC, a DC-850MHz bandwidth open loop transconductance amplifier with high impedance open collector outputs. LT5514 consists of two identical amplifiers (Figure 1). Each amplifier has an enable pin (ENA and ENB). When both amplifiers are enabled, the LT5514 operates in standard (full power-high intercept point mode). The low power mode is selected when only one amplifier is enabled. Four programmable gain inputs provide a variable attenuation of up to 22.5 dB (relative to maximum gain) with 1.5 dB steps. Amp A Attenuator Amp B Enable control Gain control logic Figure 1. LT5514 Block Diagram DC550A Demo Board 1 Quick Start Guide DEMO BOARD CONFIGURATIONS DEMO BOARD RF INPUT: TYPE RF Input: Input 1dB Freq. Range Notes Impedance A SINGLE ENDED 50 ohms 3 300 MHz 1:2 RF Input (Limited by RF input Transformer transformer) B DIFFERENTIAL 100 ohms .1 600 MHz Capacitive Differential Coupled Type A Input Amp A Input RF Transformer Variable Amp B Attenuator Enable control Gain control logic Type B Input Amp A C Variable Amp B Attenuator C Enable control Gain control logic DC550A Demo Board 2 Quick Start Guide