Overview
The AD549LH, produced by Analog Devices Inc., is a monolithic electrometer operational amplifier known for its ultralow input bias current. This amplifier utilizes Topgate™ JFET technology, a proprietary process of Analog Devices, to achieve extremely low input currents compatible with standard junction-isolated bipolar processes. The AD549LH is designed to offer precision performance with laser-trimmed input offset voltage and drift, making it suitable for applications requiring very low input current and low input offset voltage.
Key Specifications
| Parameter | AD549J | AD549K | AD549L | AD549S |
|---|---|---|---|---|
| Input Bias Current (VCM = 0 V) | 150 fA (Min), 250 fA (Typ), 420 pA (Max) | 75 fA (Min), 100 fA (Typ), 200 pA (Max) | 40 fA (Min), 60 fA (Typ), 150 pA (Max) | 75 fA (Min), 100 fA (Typ), 200 pA (Max) |
| Input Offset Voltage | 0.5 mV (Min), 1.0 mV (Typ), 1.9 mV (Max) | 0.15 mV (Min), 0.25 mV (Typ), 0.4 mV (Max) | 0.3 mV (Min), 0.5 mV (Typ), 0.9 mV (Max) | 0.3 mV (Min), 0.5 mV (Typ), 2.0 mV (Max) |
| Input Offset Voltage Drift | 10 μV/°C (Min), 20 μV/°C (Typ), 20 μV/°C (Max) | 2 μV/°C (Min), 5 μV/°C (Typ), 5 μV/°C (Max) | 5 μV/°C (Min), 10 μV/°C (Typ), 10 μV/°C (Max) | 10 μV/°C (Min), 15 μV/°C (Typ), 15 μV/°C (Max) |
| Unity Gain Bandwidth | 1 MHz | |||
| Slew Rate | 3 V/μs | |||
| Settling Time (10 V input step, 0.01% accuracy) | 5 μs | |||
| Supply Voltage | ±18 V | |||
| Operating Temperature Range | 0°C to +70°C (AD549J, AD549K, AD549L) | -55°C to +125°C (AD549S) | - | - |
Key Features
- Ultralow Input Bias Current: Achieved through Topgate™ JFET technology, ensuring very low input currents over the entire common-mode input voltage range.
- Laser-Trimmed Offset Voltage and Drift: Precision performance with input offset voltage and drift as low as 0.25 mV and 5 μV/°C, respectively.
- Low Power Consumption: Maximum quiescent supply current of 700 μA to minimize heating effects on input current and offset voltage.
- High AC Performance: 1 MHz unity-gain bandwidth and 3 V/μs slew rate, with a settling time of 5 μs to 0.01% for a 10 V input step.
- Pin Compatibility: Compatible with standard FET and electrometer op amps, allowing for easy upgrades in existing systems.
- Hermetic Packaging: Available in a TO-99 hermetic package with the case connected to Pin 8 to minimize stray leakage.
- Military Grade Options: The AD549S is specified over the military temperature range and is available processed to MIL-STD-883B, Rev. C, with extended reliability plus screening.
Applications
- Electrometer Amplifiers: Ideal for applications requiring very low input current and low input offset voltage.
- Photodiode Preamp: Excels as a preamp for current output transducers such as photodiodes and photomultiplier tubes.
- pH Electrode Buffer: Suitable for buffering pH electrodes due to its low input bias current and offset voltage.
- Vacuum Ion Gauge Measurement: Used in vacuum ion gauge measurements where low input current is crucial.
- Precision Integrator and Sample-and-Hold: Can be used as a precision integrator or low droop sample-and-hold circuit.
- Oxygen Sensors: Effective as a preamp for oxygen sensors and other current output transducers.
Q & A
- What is the primary technology used in the AD549 to achieve low input bias current?
The AD549 uses Topgate™ JFET technology, a proprietary process of Analog Devices, to achieve extremely low input currents.
- What are the typical input offset voltage and drift specifications for the AD549K?
The AD549K has a typical input offset voltage of 0.25 mV and an input offset voltage drift of 5 μV/°C.
- What is the maximum quiescent supply current of the AD549?
The maximum quiescent supply current of the AD549 is 700 μA.
- What is the unity-gain bandwidth and slew rate of the AD549?
The AD549 has a unity-gain bandwidth of 1 MHz and a slew rate of 3 V/μs.
- What is the settling time for a 10 V input step to 0.01% accuracy?
The settling time for a 10 V input step to 0.01% accuracy is 5 μs.
- What are the operating temperature ranges for the different grades of the AD549?
The AD549J, AD549K, and AD549L are rated over the commercial temperature range of 0°C to +70°C, while the AD549S is specified over the military temperature range of −55°C to +125°C.
- Is the AD549 available in military-grade options?
Yes, the AD549S is available processed to MIL-STD-883B, Rev. C, with extended reliability plus screening.
- What type of packaging is the AD549 available in?
The AD549 is available in a TO-99 hermetic package.
- Can the AD549 be used as a precision integrator or sample-and-hold circuit?
Yes, the AD549 can be used as a precision integrator or low droop sample-and-hold circuit.
- Is the AD549 pin-compatible with other FET and electrometer op amps?
Yes, the AD549 is pin-compatible with standard FET and electrometer op amps, allowing for easy upgrades in existing systems.
