Analysis of the op amp has a great influence on the rate of the power supply current?

The application described in this article takes advantage of the unique combination of features available in the LTC6261 op amp family. The low quiescent current of these devices does not impair their ability to perform operations at the power level typically reserved for more power-hungry components. On top of its versatility, features such as rail-to-rail input and output, shutdown, and package options are added.

The application described in this article takes advantage of the unique combination of features available in the LTC6261 op amp family. The low quiescent current of these devices does not impair their ability to perform operations at the power level typically reserved for more power-hungry components. On top of its versatility, features such as rail-to-rail input and output, shutdown, and package options are added.

A new family of op amps achieves industry-leading speed performance relative to supply current. The LTC6261/LTC6262/LTC6263 family (single, dual, quad) offers a 30MHz gain-bandwidth product at a low supply current of 240µA, 400µV maximum offset voltage and rail-to-rail input and output. Combined with a 1.8V to 5.25V supply, these op amps enable applications requiring uncompromised performance at low power and low voltage.

Bridged Differential Output Amplifier

Because this bandwidth and noise performance can be achieved with low supply current, achieving superior fidelity requires a fraction of the power consumption typically found in portable audio equipment. Given the unique capabilities of the LTC6261, as with active filters, revisiting headphone drivers for portable audio equipment is a reasonable plan.

Headphone speaker impedances range from 32Ω to 300Ω; their responsivity ranges from 80dB to 100dBSPL/1mW and beyond. For example, imagine a headphone speaker with a 90dBSPL/1mW responsivity that needs to draw 100mW of delivered power to achieve 110dBSPL. When its impedance is 32Ω, the RMS current is 56mA and the voltage is 1.8V; and when the impedance is 120Ω, the RMS current is 29mA and the voltage is 3.5V.

With a 3.3V supply and the output of an LTC6261 amplifier, there may not be enough drive capability to produce 100mW. However, the combination of two 180° phased amplifiers is sufficient to provide the drive capability required to achieve over 100mW of output power. Duplicate this bridge driver circuit to power the left and right sides.

The LTC6263 provides 4 amplifiers in a small package. Data obtained from a dual amplifier LTC6262 driver circuit (which can be left or right) are shown in Figures 2 and 3. The base current consumption of both amplifiers is 500µA with up to 1VP-P input and no load.

Analysis of the op amp has a great influence on the rate of the power supply current?

Figure 1: Audio Headphone Bridge Driver

Analysis of the op amp has a great influence on the rate of the power supply current?

Figure 2: LTC6262 Bridge Driver THD and Noise vs. Frequency at Different Loads

Analysis of the op amp has a great influence on the rate of the power supply current?

Figure 3: LTC6262 bridge driver THD and noise vs. amplitude (at 1kHz) under various load conditions

The circuit consists of two parts, first an inverting gain stage with closed loop gain = 1.5, and a subsequent inverting stage. The combination of inverting stages produces a single-ended input to differential output gain of 3. With a 500mVP-P input, the output is 1.5VP-P, or 0.75V max, or 0.53VRMS. A 500mV input produces approximately 5.6mW of output power when loaded into 50Ω. At 1VP-P input, the circuit provides 22.5mW. Note that this helps the LTC6261 output to have a near rail-to-rail swing under load.

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