DEMO CIRCUIT DC1103 QUICK START GUIDE DEMO CIRCUIT 1103 LOW NOISE, LOW DISTORTION DIFFERENTIAL IF AMPLIFIER QUICK START GUIDE LTC6410-6 Differential IF Amplifier DESCRIPTION Demonstration circuit 1103 features the LTC6410-6 low chain applications. The LTC6410-6 features a fully differen- noise, low distortion differential Intermediate Frequency (IF) tial input and output and is capable of directly driving a 50 Amplifier. It incorporates a variety of passive components load. One standout feature of the LTC6410-6 is the ability to to support configurations for varied applications. Single- independently adjust the input impedance with two resistors ended or differential input and output configurations are at the inputs. This allows the user to easily enhance the possible, and there is a test/calibration circuit to null out the noise figure and power gain of the system for optimal per- effects of on-board circuit components. formance. Design files for this circuit board are available. Call The LTC6410-6 is a high-speed differential amplifier with the LTC factory. 6dB of voltage gain and superior distortion and noise per- , LTC and LT are registered trademarks of Linear Technology Corporation. formance, perfect for demanding communications tran- sceivers, cellular base-stations, and other high-speed signal QUICK START PROCEDURE Table 1: DC1103 Connector Descriptions Table 1 shows the function of each SMA connector on the CONNECTOR FUNCTION board. Refer to Figure 1 for the connection diagram and J1 (-IN) Differential Input. Not connected by default. Capacitor follow the procedure below: R6 can installed and R2 removed to drive the DC1103 1. Connect the power supply as shown. The LTC6410-6 differentially. accepts supply voltages from 2.8-5.5V. The power la- J2 (+IN) Differential Input. Use this connector to supply an input to the DC1103. Drive from a 50 signal source, no ex- bels of VCC, SHDN, and GND directly correspond to ternal termination necessary. the V+, SHDN, and V- pins of the LTC6410-6, respec- TP4 (VBIAS) Self-Bias Voltage Adjust. By default, 1.45V is supplied tively. Jumper JP1 shuts down the LTC6410-6. to this pin by two resistors (VCC=3V). Override this voltage with any low-impedance DC voltage source. 2. For network analyzer use, the user can calibrate out J4 (-OUT) Differential Output. Not connected by default. Capaci- board and transformer effects using J6 and J7. tor R12 can be installed and R14 removed for differen- 3. Apply an input signal to J2. A low-distortion, low noise tial output drive. J5 (+OUT) Output. Impedance-matched to 50, can be used to signal source with an external high-order filter will yield drive a 50 network/spectrum analyzer input. the best performance (this does not apply to network J6 (TEST IN) Calibration network input. Use with a network analyzer analysis). DC1103s input is impedance-matched to to calibrate out effects of board trace parasitics, trans- 50 by default no external termination is necessary. formers, and SMA connectors. J7 (TEST OUT) Calibration network output. 4. Observe the output via J5. The output is capable of driving a 50 load, such as the input of a network or spectrum analyzer. By default, the output is imped- ance-matched to 50. 1 DEMO CIRCUIT DC1103 QUICK START GUIDE LOW NOISE, LOW DISTORTION DIFFERENTIAL IF AMPLIFIER Proper Measurement Equipment Setup ADDITIONAL INFORMATION Although the DC1103 demo board is ready to use out of the The output SMA connectors are spaced 0.8 (20.32mm) box, it has features that you can access by adding, remov- apart, suitable for direct connection to various Linear Tech- ing or changing components on the board. This and other nology amplifier/ADC-driver demo boards such as DC800 important board information are included in this section. (LT1993) and DC987 (LTC6400, LTC6401). DIFFERENTIAL INPUTS ADJUSTING THE INPUT IMPEDANCE To drive the inputs differentially, remove capacitor C31 and The input impedance of the LTC6410 can be adjusted in the install C26. J1 and J2 can now be driven differentially from range of 58-2000 by replacing R5 and R6 with equal- a 50 signal source. The input to the DC1103 will still be value non-zero resistors. The correct resistor value for the matched to 50 (differential) when driven in this manner. desired differential input impedance is: (3810 Z ) 220000 DIFF SMA CONNECTOR SPACING R ,R = 5 6 The input SMA connectors are spaced 0.6 (15.24mm) 2000 Z DIFF apart, suitable for direct connection to the DC1119 demo Adjusting the input impedance too high may affect the board for Linear Technologys LT5527, LT5557, and performance of the part. See the LTC6410 datasheet. LT5559 high linearity downconverting mixers. 2