HGSEMI Operational Amplifiers

Gain bandwidth product (GBW) is the frequency at which the op-amp's open-loop gain drops to unity (1). For closed-loop applications, the available bandwidth is GBW divided by closed-loop gain. For example, an op-amp with 1MHz GBW configured for gain of 10 has bandwidth of 100kHz. Select GBW at least 10-20x higher than your signal frequency for adequate gain margin. For a 10kHz signal with gain of 10, you need GBW > 1-2MHz. Higher GBW provides more bandwidth but typically consumes more power.

Calculate required GBW as 10-20x (signal frequency × closed-loop gain). Contact our FAE team for op-amp selection based on your signal characteristics.

Input offset voltage (Vos) is the differential DC voltage required between the input terminals to make the output zero. It's caused by manufacturing mismatches in the input transistor pair. Vos is important in precision DC applications like sensor signal conditioning, current sensing, and instrumentation. For example, with 1mV Vos and gain of 100, the output has 100mV error. General purpose op-amps have Vos of 1-5mV

precision op-amps have Vos < 1mV, down to microvolts for zero-drift types. Select precision op-amps when DC accuracy is critical.

For DC accuracy requirements, calculate allowable Vos based on gain and accuracy needs. Our FAE team can recommend precision op-amps for your accuracy requirements.

Slew rate is the maximum rate of change of the op-amp output voltage, typically specified in V/μs. It limits how fast the output can respond to large input changes. If the required output change exceeds the slew rate, the output distorts (slew limiting). For a sine wave, maximum slew rate required is 2πfVp, where f is frequency and Vp is peak voltage. For example, a 100kHz sine wave with 5V peak requires slew rate > 3.14V/μs. Select op-amp with slew rate at least 2-3x the calculated requirement for margin.

Calculate required slew rate based on signal frequency and amplitude. Select op-amp with adequate margin. Contact our FAE team for high-speed op-amp recommendations.

Rail-to-rail input (RRI) op-amps allow input voltage to extend to or beyond the supply rails, important for low-voltage applications with large input signals. Rail-to-rail output (RRO) op-amps can swing output close to supply rails (within 10-100mV), maximizing dynamic range in low-voltage systems. Standard op-amps may have 1-2V headroom from each rail. For 3.3V single-supply systems, RRO provides much more output swing. Many modern op-amps have both RRI and RRO (RRIO), providing maximum flexibility in low-voltage designs.

For low-voltage single-supply applications, use RRIO op-amps. For split-supply or higher voltage, standard op-amps may suffice. Our FAE team can recommend rail-to-rail op-amps.

Single op-amps (1 per package) offer flexibility in placement and routing but take more board area. Dual op-amps (2 per package) provide good density for stereo or differential circuits. Quad op-amps (4 per package) offer highest density for multi-channel applications. Consider: Board space constraints - quads most compact

Circuit topology - duals convenient for differential amplifiers

Thermal considerations - singles dissipate heat better

and Inventory management - singles most flexible. For mixed applications, using singles may simplify BOM, while duals/quads reduce package count.

Consider board space, thermal requirements, and circuit topology. Our FAE team can help optimize package selection for your design.