TLC2252CD

The TLC2252CD is a dual rail-to-rail output very low-power operational amplifier from Texas Instruments, built on the Advanced LinCMOS process. It is part of the TLC225x family, which includes the TLC2252 (dual) and TLC2254 (quad) variants. The device is fully characterized at both 5V and ±5V supply voltages and optimized for low-voltage, battery-powered applications.

The TLC2252 features rail-to-rail output swing that includes both supply rails, maximizing dynamic range in single-supply or split-supply configurations. The common-mode input voltage range extends to the negative rail (V-), enabling direct ground-referenced sensing in single-supply systems. Each channel consumes only 35 µA of supply current (typical), making it one of the lowest-power dual op-amps available in its class.

Key specifications include a gain-bandwidth product of 200 kHz, a slew rate of 0.12 V/µs, input offset voltage of 1.5 mV max (850 µV for the A-grade TLC2252A), input bias current of 1 pA typical (60 pA max), and equivalent input noise of 19 nV/√Hz at 1 kHz. The low input bias current, a characteristic of the CMOS input stage, makes the TLC2252 ideal for high-impedance signal conditioning from sources such as piezoelectric transducers, photodiodes, and pH probes.

The CD suffix denotes the SOIC-8 plastic surface-mount package rated for the commercial temperature range of 0°C to +70°C. The D package code refers to the standard 8-pin SOIC (Small Outline Integrated Circuit) with gull-wing leads. The tube packaging option is standard for this variant. The TLC2252CD supports both single-supply (4.4V to 16V) and dual-supply (±2.2V to ±8V) operation, providing flexibility across a wide range of analog signal conditioning applications.

Compared to earlier generation micropower CMOS op-amps such as the TLC27L2 or TS27L2, the TLC2252 offers significantly improved noise performance (19 nV/√Hz vs typical >50 nV/√Hz), rail-to-rail output for increased dynamic range, and lower input offset voltage. For precision applications requiring tighter offset, the TLC2252A variant offers 850 µV max offset at 25°C.

The TLC2252CD operates as a dual-channel CMOS operational amplifier using Texas Instruments Advanced LinCMOS process, combining micropower consumption with rail-to-rail output capability.

CMOS Input Stage: The input stage uses a differential pair of P-channel MOSFETs, providing extremely high input impedance (typically 10^12 Ω) and very low input bias current (1 pA typical). This CMOS input architecture eliminates the input bias current errors that plague bipolar op-amps in high-impedance circuits. The input common-mode voltage range extends from the negative rail (V-) to approximately 1.2V below the positive rail (V+), enabling ground-referenced operation in single-supply applications. The input offset voltage is laser-trimmed to 850 µV max (A-grade) or 1.5 mV max (standard grade) at 25°C.

Rail-to-Rail Output Stage: The output stage uses a complementary CMOS push-pull configuration with both P-channel and N-channel output transistors. This architecture allows the output to swing to within millivolts of both supply rails under light load conditions (typically 10 mV from V- and 60 mV from V+ with 100 kΩ load). The rail-to-rail output maximizes the usable signal range in single-supply applications, which is critical when interfacing with ADCs where even a few hundred millivolts of lost dynamic range can significantly reduce resolution.

Micropower Operation: The TLC2252 achieves its very low supply current (35 µA per channel, 80 µA total for dual) through careful biasing of the internal gain stages at very low quiescent current levels. This micropower design makes the device ideal for battery-powered applications where supply current must be minimized. The trade-off for low power is reduced bandwidth (200 kHz GBW) and slew rate (0.12 V/µs), which are adequate for DC and low-frequency signal conditioning.

Gain-Bandwidth Product: The 200 kHz gain-bandwidth product defines the frequency at which the open-loop gain drops to unity (0 dB). For a closed-loop gain of 10 (20 dB), the bandwidth is approximately 20 kHz; for a gain of 100 (40 dB), approximately 2 kHz. The TLC2252 is therefore best suited for DC and low-frequency applications such as sensor signal conditioning, transducer amplification, and active filtering below audio frequencies.

Slew Rate: The 0.12 V/µs slew rate limits the maximum output swing at high frequencies. For a full-scale sine wave output, the maximum frequency before slew-rate limiting is f_max = SR / (2π × Vp), where Vp is the peak output voltage. For a 5V peak-to-peak output (Vp = 2.5V), the maximum frequency is approximately 7.6 kHz. This is consistent with the device target application space of DC and low-frequency signal conditioning.

Noise Performance: The TLC2252 achieves 19 nV/√Hz input-referred voltage noise at 1 kHz, which is approximately four times lower than competing micropower CMOS op-amps. This improvement is achieved through optimized input transistor sizing and bias current distribution. The low noise, combined with the high input impedance, makes the device excellent for amplifying small signals from high-impedance sources such as piezoelectric sensors and photodiodes without significant noise degradation.