Operationsforstærkere til højt ydende TIA og buffer løsninger
LTC6268 og LTC6269 fra Linear Technology er FET-input operationsforstærkere (single og dual), som tilbyder fremragende ydelse i højhastigheds og højdynamiske TIA (transimpedance amplifier) og buffer applikationer (in english).
Sensors convert real world signals such as temperature, light, pressure, and radio waves into electric currents and voltages which can then be processed by electronic circuits to do all kinds of wonderful things in medical, industrial, automotive, and consumer applications.However many sensors do not have the drive capability (output impedance) or output voltage range to directly drive an ADC or other monitor/control circuits. Amplifier circuits play an important role in buffering and scaling (or conditioning) a sensor’s output signal.
The choice of circuit topology and the specific amplifier will depend on the properties of the sensor. Photodiodes are a popular choice for converting light to an electrical signal – usually a small current. The amplifier topology of choice is the Transimpedance Amplifier (TIA) which uses an op amp and a feedback resistor to convert the current to a scaled and buffered voltage.
A good high speed TIA requires several things: high gain-bandwidth product, ultralow input bias current, low input capacitance, and low wideband voltage and current noise. These attributes are difficult to achieve simultaneously but they come together in the LTC6268 and LTC6269 single and dual operational amplifiers from Linear Technology to create very high performance TIA and buffer solutions.
With just 3fA bias current at 25°C and 4pA max over the entire –40°C to 125°C temperature range, the LTC6268/LTC6269 can resolve input currents from several femtoamps to amps. Wideband voltage and current noise is 4.3nV/√Hz and 5.5fA/√Hz, respectively, enabling high dynamic range circuits.
Built for speed as well as precision, the LTC6268 features 500MHz gain bandwidth product, sub-pF input capacitance and –100dB harmonic distortion at 1MHz. In addition to photodiode and photomultiplier (PMT) circuits, the LTC6268/9 are well suited for other high impedance sensor applications and for driving analog-to-digital converters (ADCs).
The LTC6268 data sheetfeatures circuit and layout techniques to maximize TIA performance, with example circuits ranging from 20kΩ transimpedance gain at 65MHz bandwidth, to 499kΩ transimpedance gain at 11.2MHz bandwidth.
The LTC6268 is available in a 6-lead SOT-23 package, as well as an 8-lead SOIC with guard pins to protect against board leakage currents. The LTC6269 is available in MSOP-8 with exposed pad and 3mm x 3mm DFN-10 packages.
The LTC6268 and LTC6269 are unity-gain stable and fully specified over the industrial –40°C to 85°C and –40°C to 125°C temperature ranges.
www.linear.com/product/LTC6268 and
www.linear.com/product/LTC6269
