Electronic Components Datasheet Search |
|
PGA207 Datasheet(PDF) 8 Page - Burr-Brown (TI) |
|
|
PGA207 Datasheet(HTML) 8 Page - Burr-Brown (TI) |
8 / 10 page 8 ® PGA206/207 FIGURE 2. Optional Offset Voltage Trim Circuits. R1 adjusts the offset of the input amplifiers. Output stage offset is adjusted with R2. A buffer op amp is required in the output offset adjustment circuit, as shown, to assure that the Ref pin is driven by a low source impedance. To adjust for low offset voltage in all gains, first adjust the input stage offset in the highest gain. Then adjust the output stage offset (R2) in G = 1. Iterate the adjustments for lowest offset in all gains. Offset can also be adjusted under processor control with a D/A converter as shown in Figure 2. The D/A’s output voltage can be reduced with a resistor divider for better adjustment resolution, but an op amp buffer following the divider is required to provide a low source impedance to the ref terminal. A different offset value is required for each amplifier gain. INPUT BIAS CURRENT RETURN PATH The FET inputs of the PGA206 and PGA207 provide ex- tremely high input impedance. Still, a path must be provided for the bias current of each input. Figure 3 shows provisions for an input bias current path. Without a bias current return path, the inputs will float to a potential which exceeds the linear input voltage range and the input amplifiers will saturate. If the differential source resistance is low, a bias current return path can be connected to only one input (see thermo- couple example in Figure 3). With higher source impedance, using two resistors provides a balanced input with possible advantages of lower input offset voltage due to bias current and better common-mode rejection. Many sources or sensors inherently provide a path for input bias current (e.g. the bridge sensor shown in Figure 3). These applications do not require additional resistor(s) for proper operation. FIGURE 3. Providing an Input Bias Current Path. 47k Ω 47k Ω 10k Ω Microphone, Hydrophone etc. Thermocouple Center-tap provides bias current return. V R Bridge Bias current return inherrently provided by source. PGA PGA PGA PGA A 1 A 2 A 3 12 11 10 10k Ω 10k Ω 10k Ω 10k Ω 7 PGA206 PGA207 Resistors can be substituted for REF200. Power supply rejection will be degraded. Digitally Selected Feedback Network 6 V O2 V+ V O OPA131 D/A V+ R 2 10k Ω 100 Ω 100 Ω V– V REF 5 14 16 4 V IN V IN – + 15 A 1 A 0 Digital Ground Optional Input Offset Adjustment 13 V+ 1 V O1 9 8 V– Over-Voltage Protection Over-Voltage Protection 100µA 1/2 REF200 100µA 1/2 REF200 Offset control with digital/analog converter Manual output offset trim circuit. 200k Ω (100k Ω to 500kΩ) R 1 |
Similar Part No. - PGA207 |
|
Similar Description - PGA207 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |