Automotive designs are increasingly employing brushless dc (BLDC) motors and electronic control units (ECUs) for advanced driver-assistance systems (ADAS). These require precision op amps for accurate analog signal conditioning.
On that front, Diodes Inc. has released operational amplifiers featuring input offset stabilization for automotive signal-conditioning applications.Input offset voltage is defined as the voltage that must be applied between the two input terminals of the op amp to obtain 0 V at the output.
Ideally, if both inputs of an op amp are at exactly the same voltage, then the output should be at 0 V. In practice, though, a small differential voltage must be applied to the inputs to force the output to zero. This is known as the input offset voltage (VOS).
Chopper-Stabilized Op Amp
Diodes’ AS333Q is an automotive high-precision operational amplifier designed with chopping stabilization techniques that eliminate 1/f noise as well as the crossover distortion presented in most rail-to-rail input and output (RRIO) amplifiers. A chopper-stabilized amplifier employs a modulation technique to reduce or eliminate dc offset and low-frequency noise in op amps.
The chopping amplifier utilizes switches to chop or modulate the input signal. The output is then filtered, summed, and fed back to the inputs of the main and chopper amplifiers to remove low-frequency errors from the circuit.
The AS333Q is a single-channel version of the dual-channel AS2333Q op amp designed for current sensing and signal detection in a broad range of in-vehicle functions. These include airbags, position sensors, vehicle occupant detection sensors, on-board chargers (OBCs) wireless chargers, and battery-management systems (BMS).
According to the company, the chopper-stabilized low input offset voltage and almost zero temperature drift (0.02 µV/°C) of the AS333Q enable it to maintain high accuracy across the full common-mode input voltage range.
Dual CMOS Op Amp
Similarly, the AS2333Q is a dual CMOS operational amplifier also designed with chopping stabilization techniques. It can provide low input offset voltage (8 μV typical) and near zero-drift over time and temperature.
The low-quiescent-current amplifier offers high-impedance inputs that have a common-mode range of 100 mV beyond the rails, and rail-to-rail output that swings within 50 mV of the rails. Single or dual supplies as low as 1.8 V (±0.9 V) and up to 5.5 V (±2.75 V) can be used.
The AS2333Q comes in a standard 8-pin SO-8 package. The device is AEC-qualified for automotive applications and is temperature grade 1 (−40 to +125°C).
The AS333Q provides not only maximum output voltage swing capability, but again an extended 100-mV common-mode voltage beyond the supply rail. The device is fully specified to operate from 1.6- to 5.0-V single-supply, or ±0.8- and ±2.5-V dual-supply applications.
The device offers 350-kHz gain bandwidth while consuming only 17-μA quiescent current. This means it can be used in equipment that must continue operating while a vehicle’s engine is off. With low input offset voltage (8 μV) and zero-drift offset voltage (0.02 μV/°C), it’s well-suited for applications that require precision, especially low-power varieties.
In addition, the device’s ability to handle beyond-the-rail-to-rail common-mode inputs allows the AS333Q to support both supply and ground-referenced inputs. Its 1.1-µV/√Hz low-frequency noise helps to improve signal-to-noise ratios.
- Low input offset voltage: 8 μV (typ)
- Zero drift: 0.02 μV/°C (typ)
- 0.1- to 10-Hz noise: 1.1 μV p-p
- Low quiescent current: 17 μA (typ)
- Supply voltage: 1.8 to 5.5 V
- Operation ambient temperature range: −40 to +125°C
- ESD protection: JESD 22, 4000-V HBM (A114)
The AS333Q, which comes in a SOT25 package, is AEC-Q100 qualified for automotive applications. It’s manufactured in IATF16949-certified facilities.