HF2TA Key Features
- 50 MHz frequency range for wide range of applications
- 2 independent amplification channels
- Wide range of precision transimpedance gain settings (100 V/A to 100 MV/A)
- Integrated offset adjustment / compensation
- Extremely low noise and low input leakage
- Bias output for sensor power
- Dedicated interface to HF2 Instruments (no direct PC link)
HF2TA Compatible Instruments
- General current amplifier (physics, biology, engineering)
- Accurate impedance measurements / 4 point measurements
- Scanning probe microscopy
- Electrical impedance spectroscopy (EIS)
- Electrical impedance tomography (EIT)
- Photodiode current amplification
HF2TA Functional Diagram
Providing 2 input and 2 output connectors, the HF2TA features a transimpedance architecture with a variable precision resistor as the gain parameter (R). The transimpedance architecture matches the current through the feedback resistor and keeps the input at virtual ground. The second amplification stage provides decoupling from the first stage and an additional gain (G). The resulting output voltage corresponds to U = R * G * I.
JFET Input Amplifier
The input of the HF2TA is constructed with JFET amplifiers which provide very low-noise over a wide frequency range. Additionally, the ultra-low input bias current of typically 2 pA allows for precise current measurements at small signal amplitudes.
Input Offset Adjust
To account for unbalanced circuitry inside the operation amplifiers and to cope with other external sources of voltage offset, the HF2TA provides a specific compensation feature with a very fine granularity. The user simply adjusts for a previously measured offset inside the graphical user interface of the HF2 Instrument.
Bias Input and Auxiliary Output
The Bias Input allows driving the signal shields with defined bias voltage. This can be used for instance to power a photo diode connected with one shielded cable for power and signal, avoiding ground loops. The Aux Output provides a low-noise power source able to run an external sensor or detector. The maximum output power is 100 mW.
Single Connector to HF2 Instruments
The HF2TA fits to any HF2 Instrument with its single connector, providing both power supply and remote control. The HF2TA is automatically detected by the Instrument when it is connected and all settings can be controlled from the graphical user interface.
Current Amplifier Settings
Configurable settings include the transimpedance (R1, R2), the output voltage gain (G1, G2), the switch to control signal shield bias, the AC/DC coupling switch to suppress DC current offsets, the offset voltage compensation adjustment and the output bias voltage.
|frequency range (3 dB cut-off)||DC - 50 MHz (depends on R1,R2 settings)|
|frequency range with AC coupling||10 Hz - 50 MHz (depends on R1,R2 settings)|
|small signal bandwidth (0.1 Vpp)||50 MHz|
|large signal bandwidth (1 Vpp)||40 MHz|
|input current range||1 nA - 10 mA (depends on R1,R2,G1,G2 settings)|
|input noise current||50 fA - 150 pA (depends on R1,R2,G1,G2 settings)|
|input noise voltage (10 kHz)||5 nV/√Hz|
|input offset adjustment range||±10 mV|
|input current leakage (typical)||2 pA|
|input impedance (DC, Z // 15 pF)||50 Ω - 70 kΩ|
|input bias voltage range||±10 V|
|transimpedance gain (R1,R2)||100 V/A - 100 MV/A|
|output voltage gain (G1,G2)||G=1 or G=10|
|typical use||bias for external sensor (ex: photodetectors)|
|voltage range||±10 V|
|maximum current drive||10 mA|