Datasheet

1-1

Introduction and Description

The Texas Instruments THS3061 evaluation module (EVM) helps designers

evaluate the performance of the THS3061 operational amplifier. Also, this

EVM is a good example of high-speed PCB design.

This document details the THS3061EVM. It includes a list of EVM features, a

brief description of the module illustrated with a series of schematic diagrams,

EVM specifications, details on connecting and using the EVM, and a discus-

sion of high-speed amplifier design considerations.

This EVM enables the user to implement various circuits to clarify the available

configurations presented by the schematic of the EVM. The user is not limited

to the circuit configurations presented here. The EVM provides enough hard-

ware hooks that the only limitation should be the creativity of the user.

1.1 Evaluation Schematic

As delivered, the EVM has a fully functional example circuit—just add power

supplies, a signal source, and monitoring instrument. See Figure 1–1 for the

complete (default) EVM schematic showing all component locations. The user

can change the gain by changing the ratios of the feedback and gain resistors

(see the device data sheet for recommended resistor values).

The default configuration is designed to provide for a voltage gain of –1 and

about +2 depending on which input is connected to the signal source. This volt-

age gain is the ratio of the voltage at the output pin of the amplifier (pin 6) to

the voltage at the input at J1 or J2 respectively.

For optimum frequency response and stability at either –1 or +2 gain, a 562-Ω

feedback resistor was chosen for R5. The same value is set for R3 to provide

a gain in the inverting configuration of –1. To match the signal generator source

impedance, R2 is set to 54.9 Ω. This is the closest value, when placed in paral-

lel with R3 (562 Ω) that terminates the inverting input to 50 Ω).

Output series resistor R6 is set to 49.9 Ω. This value terminates the output cor-

rectly for connection to a 50-Ω input device, as shown in the applications de-

scribed in Chapter 3. Setting R7 to 953 Ω loads the amplifier at about 1 kΩ, to

match a high-impedance instrument connected to the output connector J4.

Chapter 1