Electronic Components Datasheet Search |
|
OPA177GSG4 Datasheet(PDF) 7 Page - Texas Instruments |
|
|
OPA177GSG4 Datasheet(HTML) 7 Page - Texas Instruments |
7 / 11 page 7 ® OPA177 APPLICATIONS INFORMATION The OPA177 is unity-gain stable, making it easy to use and free from oscillations in the widest range of circuitry. Ap- plications with noisy or high impedance power supply lines may require decoupling capacitors close to the device pins. In most cases 0.1 µF ceramic capacitors are adequate. The OPA177 has very low offset voltage and drift. To achieve highest performance, circuit layout and mechanical conditions must be optimized. Offset voltage and drift can be degraded by small thermoelectric potentials at the op amp inputs. Connections of dissimilar metals will generate ther- mal potential which can mask the ultimate performance of the OPA177. These thermal potentials can be made to cancel by assuring that they are equal in both input terminals. 1. Keep connections made to the two input terminals close together. 2. Locate heat sources as far as possible from the critical input circuitry. 3. Shield the op amp and input circuitry from air currents such as cooling fans. OFFSET VOLTAGE ADJUSTMENT The OPA177 has been laser-trimmed for low offset voltage and drift so most circuits will not require external adjust- ment. Figure 1 shows the optional connection of an external potentiometer to adjust offset voltage. This adjustment should not be used to compensate for offsets created elsewhere in a system since this can introduce excessive temperature drift. INPUT PROTECTION The inputs of the OPA177 are protected with 500 Ω series input resistors and diode clamps as shown in the simplified circuit diagram. The inputs can withstand ±30V differential inputs without damage. The protection diodes will, of course, conduct current when the inputs are overdriven. This may disturb the slewing behavior of unity-gain follower applica- tions, but will not damage the op amp. NOISE PERFORMANCE The noise performance of the OPA177 is optimized for circuit impedances in the range of 2k Ω to 50kΩ. Total noise in an application is a combination of the op amp’s input voltage noise and input bias current noise reacting with circuit impedances. For applications with higher source impedance, the OPA627 FET-input op amp will generally provide lower noise. For very low impedance applications, the OPA27 will provide lower noise. INPUT BIAS CURRENT CANCELLATION The input stage base current of the OPA177 is internally compensated with an equal and opposite cancellation cur- rent. The resulting input bias current is the difference between the input stage base current and the cancellation current. This residual input bias current can be positive or negative. When the bias current is cancelled in this manner, the input bias current and input offset current are approximately the same magnitude. As a result, it is not necessary to balance the DC resistance seen at the two input terminals (Figure 2). A resistor added to balance the input resistances may actu- ally increase offset and noise. FIGURE 1. Optional Offset Nulling Circuit. OPA177 V 2 3 1 8 Trim Range is approximately ±3.0mV V+ 20k Ω OUT V IN Op Amp (a) R B OPA177 (b) No bias current cancellation resistor needed Conventional op amp with external bias current cancellation resistor. OPA177 with no external bias current cancellation resistor. = R 2 || R1 R 2 R 1 R 2 R 1 FIGURE 2. Input Bias Current Cancellation. |
Similar Part No. - OPA177GSG4 |
|
Similar Description - OPA177GSG4 |
|
|
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 |