Wide-bandwidth data-acquisition (DAQ) systems (for example, oscilloscopes and active probes) use an analog front end (AFE) signal chain to capture high-frequency signals and fast-transient pulses. The input amplifier is the first stage in the signal chain of a wide-bandwidth DAQ system. The high input impedance (high-Z) and low bias current inputs of a JFET-input amplifier allow the measurement of small signals and help set the noise floor of the entire signal chain. JFET amplifiers are used as either unity-gain buffers (Figure 1) or in noninverting gain configurations (Figure 2) between the analog input signal and the analog-to-digital converter (ADC).
Parameter | BUF802 | OPA818 | OPA859 | OPA817 | OPA814 |
---|---|---|---|---|---|
VS MIN to MAX (V) | 9 to 13 | 6 to 13 | 3.3 to 5.25 | 6 to 12.6 | 6 to 12.6 |
Large Signal Bandwidth (2VPP) (MHz) | 1600 | 400 | 400 | 250 | 200 |
Slew rate (V/μs) | 7000 | 1400 | 1150 | 100 | 700 |
Input impedance (GΩ) | 50 | 500 | 1 | 60 | 60 |
Noise (nV/√Hz) | 2.3 | 2.2 | 3.3 | 4.5 | 5.3 |
Maximum Drift (μV/°C) | 1330(1) | 20 | N/A | 3.5 | 3.5 |
Fixed Gain (V/V) | Yes | No | No | No | No |
Maximum Bias Current (pA) | 25 | 25 | 5 | 20 | 20 |
Output Voltage Swing (V) | VS+ – 1.9, VS– + 3.4 |
VS+ – 0.5, VS– + 0.5 |
VS+ – 0.9, VS– + 2.2 |
±3.9 | ±3.9 |
IQ (TYP) (mA) | 34 | 27.7 | 20.5 | 23.5 | 16 |
Smallest Package Size (mm) | VQFN 3 × 3 |
WSON 3 × 3 |
WSON 3 × 3 |
WSON 3 × 3 |
SOT-23 2.9 × 2.8 |
Parameter | THS4631 | OPA810 |
---|---|---|
VS Min to Max (V) | 10 to 32 | 4.75 to 24 |
Large Signal BW (2VPP) (MHz) | 230 | 70 |
Slew rate (V/μs) | 1000 | 200 |
Input impedance (GΩ) | 10 | 12 |
Noise (nV/√Hz) | 7 | 6.3 |
Maximum Drift (μV/℃) | 10 | 10 |
Fixed Gain (V/V) | No | No |
Max Bias Current (pA) | 100 | 20 |
Output Voltage Swing (V) | ±13.5 | VS+ – 0.11, VS– + 0.08 |
IQ (typ) (mA) | 11.5 | 3.7 |
Smallest Package Size (mm) | HVSSOP 3 × 4.9 |
SC70 2 × 1.25 |
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