SLOS073 Data sheet

SLOS073H March 1976 – October 2024 RC4558

PRODUCTION DATA

7.2.2 Detailed Design Procedure

The circuit in Figure 7-1 takes a single-ended input signal, V_IN, and generates two output signals, V_OUT+ and V_OUT–, using two amplifiers and a reference voltage, V_REF. V_OUT+ is the output of the first amplifier and is a buffered version of the input signal, V_IN (see Equation 1). V_OUT– is the output of the second amplifier which uses V_REF to add an offset voltage to V_IN and feedback to add inverting gain. The transfer function for V_OUT– is Equation 2.

Equation 1.

V_{O U T +} = V_{I N}

Equation 2.

V_{O U T -} = V_{R E F} \times (\frac{R_{4}}{R_{3} + R_{4}}) \times (1 + \frac{R_{2}}{R_{1}}) - V_{I N} \times \frac{R_{2}}{R_{1}}

The differential output signal, V_DIFF, is the difference between the two single-ended output signals, V_OUT+ and V_OUT–. Equation 3 shows the transfer function for V_DIFF. By applying the conditions that R₁ = R₂ and R₃ = R₄, the transfer function is simplified into Equation 6. Using this configuration, the maximum input signal is equal to the reference voltage and the maximum output of each amplifier is equal to the V_REF. The differential output range is 2 × V_REF. Furthermore, the common-mode voltage is one half of V_REF (see Equation 7).

Equation 3.

V_{D I F F} = V_{O U T +} - V_{O U T -} = V_{I N} \times (1 + \frac{R_{2}}{R_{1}}) - V_{R E F} \times (\frac{R_{4}}{R_{3} + R_{4}}) (1 + \frac{R_{2}}{R_{1}})

Equation 4.

V_{O U T +} = V_{I N}

Equation 5.

V_{O U T -} = V_{R E F} - V_{I N}

Equation 6.

V_{D I F F} = 2 \times V_{I N} - V_{R E F}

Equation 7.

V_{C M} = (\frac{V_{O U T +} + V_{O U T -}}{2}) = \frac{1}{2} V_{R E F}