Opamps for Sensor Signal Amplification
Enables improved signal processing accuracy at lower supply voltages

ROHM has developed the BD5291G and the BD5291FVE  low voltage, low offset opamps which are designed to amplify signals from motion sensors such as accelerometers and gyroscopes.

Recent years have seen a growing number of devices, such as smartphones, tablet PCs, and portable gaming systems, incorporate sensors to detect acceleration, angular velocity, and other parameters. Sensors are devices often embedded in applications that convert physical changes to small electrical signals. To make use of these small signals, however, they must be amplified using sensor signal amplifiers, which are positioned downstream of the sensor and require sensitive analog technology to ensure high-accuracy amplification.

Both the BD5291G and BD5291FVE utilize ROHM's industry-leading analog technology, enabling input/outputfull-swing operation at only 1.7V. In addition, a high common-mode rejection ratio results in a small-signal processing accuracy that is 18 times better than what can be achieved with ordinary low voltage operational amplifiers.

Key Features
1. Low voltage operation with input full-swing Low-voltage input / output full-swing operation is ideal for applications with low supply-voltage requirements.	2．High accuracy signal amplification Low input offset voltage combined with high common-mode rejection ratio (70dB min) makes it possible to amplify small signals (i.e. from sensors) with greater accuracy.

ROHM opamps provide low voltage operation with input/output full-swing capability and high common-mode rejection ratio (conventionally difficult to achieve all 3), contributing to greater accuracy in small-signal applications such as sensor signal amplification. These opamps are also well-suited for microphone amplifiers, active filters, buffer amps, bridge amplifier circuits, and other applications utilizing low voltage opamps.

Increasing integration of digital and analog systems has resulted lower power supply voltages. Unlike conventional input/output full-swing opamps that operate from 1.8V, these products support 1.7V operation, providing sufficient margin against supply voltage fluctuations. In addition, common-mode rejection ratio is 70dB (min), compared to only 45dB (min) with comparable devices, making it possible to provide high-accuracy signal amplification. ( 45dB and 70dB are roughly equivalent to 178x and 3,162x, respectively, yielding 18x improvement.)

Pricing: BD5291FVE-GTR $0.157 (min 3000 pcs) BD5291G-GTL $0.267 (min 3000 pcs) Availability: Now Applications ◇Smartphones ◇Tablet PCs ◇Portable CD/DVD players ◇Handheld gaming equipment and other devices utilizing motion sensors ◇Microphone amps ◇Active filters ◇Buffer amps ◇Amplification circuits ◇General-purpose, low voltage opamp applications

Specifications

Part No.	Supply Voltage Range (VDD) [V]	Input/Output Range [V]	CMRR (Min)[dB]	Input Offset Voltage (Max) [mV]	Package Type	Package Size [mm]
BD5291G	1.7 ～ 5.5	0 ～ VDD	70	±2.5	SSOP5	2.9 x 2.8 x 1.25
BD5291FVE					VSOF5	1.6 x 1.6 x 0.6
Conventional	1.8 ～ 5.5	0 ～ VDD	45	±9	SSOP5	2.9 x 2.8 x 1.25

Input/Output Full-Swing CMOS Opamp Lineup

Terminology

1. Input/Output Full Swing
   Enables signal input/output from the lower (VSS) to the upper (VDD) supply voltage limits. Generally, the maximum output voltage amplitude in standard opamps is typically 1-2V below VDD and above VSS. As a result, circuit operation is not possible within these regions. For low operating supply voltages, this makes the input voltage range relatively narrow, providing insufficient margin for the output voltage. In contrast, input/output full-swing opamps support input and output voltages throughout the entire supply voltage range, from VSS to VDD, ensuring adequate margin even at lower voltage operation.


2. Common-Mode Rejection Ratio (CMRR)
   Inputting the exact same signal (common-mode) into both input pins of an amp (amplifier) should ideally yield an output of zero. However, the input offset voltage of the amplifier is also amplified. Common-mode rejection ratio indicates the ability of the opamp to reject the common mode signal. Opamps with a high CMRR are normally selected for amplifying a small signal riding on a common-mode voltage.

Input/Output Full Swing OpAmps for Motion Sensors BD5291 Series (298KB)