9.1 Overview

The THS4541-Q1 is a voltage-feedback (VFA) based, fully-differential amplifier (FDA) offering greater than 500-MHz, small-signal bandwidth at a gain of 2 V/V with trimmed supply current and input offset voltage. The core differential amplifier is a slightly decompensated voltage-feedback design with a high slew-rate, precision input stage. This design gives the 500-MHz gain of 2-V/V small-signal bandwidth shown in the characterization curves, with a 1500-V/µs slew rate, yielding approximately a 340-MHz, 2-V_PP, large-signal bandwidth in the same circuit configuration.

The outputs offer near rail-to-rail output swing (0.2-V headroom to either supply), while the device inputs are negative rail inputs with approximately 1.2 V of headroom required to the positive supply. This negative rail input directly supports a bipolar input around ground in a DC-coupled, single-supply design (see Figure 63). Similar to all FDA devices, the output average voltage (common-mode) is controlled by a separate common-mode loop. The target for this output average is set by the Vocm input pin that can be either floated to default near midsupply or driven to a desired output common-mode voltage. The Vocm range extends from a very low 0.91 V above the negative supply to 1.1 V below the positive supply, supporting a wide range of modern analog-to-digital converter (ADC) input common-mode requirements using a single 2.7-V to 5.4-V supply range for the THS4541-Q1.

A power-down pin (PD) is included. Pull the PD pin voltage to the negative supply to turn the device off, putting the THS4541-Q1 into a very-low quiescent current state. For normal operation, the PD pin must be asserted high. When the device is disabled, remember that the signal path is still present through the passive external resistors. Input signals applied to a disabled THS4541-Q1 still appear at the outputs at some level through this passive resistor path as they would for any disabled FDA device.