Electronic Components Datasheet Search |
|
OPA627AUE4 Datasheet(PDF) 11 Page - Texas Instruments |
|
|
OPA627AUE4 Datasheet(HTML) 11 Page - Texas Instruments |
11 / 16 page 11 ® OPA627, 637 INPUT PROTECTION The inputs of the OPA627/637 are protected for voltages between +V S + 2V and –VS – 2V. If the input voltage can exceed these limits, the amplifier should be protected. The diode clamps shown in Figure 7a will prevent the input voltage from exceeding one forward diode voltage drop beyond the power supplies—well within the safe limits. If the input source can deliver current in excess of the maxi- mum forward current of the protection diodes, use a series resistor, R S, to limit the current. Be aware that adding resistance to the input will increase noise. The 4nV/ √Hz theoretical thermal noise of a 1k Ω resistor will add to the 4.5nV/ √Hz noise of the OPA627/637 (by the square-root of the sum of the squares), producing a total noise of 6nV/ √Hz. Resistors below 100 Ω add negligible noise. Leakage current in the protection diodes can increase the total input bias current of the circuit. The specified maxi- mum leakage current for commonly used diodes such as the 1N4148 is approximately 25nA—more than a thousand times larger than the input bias current of the OPA627/637. Leakage current of these diodes is typically much lower and may be adequate in many applications. Light falling on the junction of the protection diodes can dramatically increase leakage current, so common glass-packaged diodes should be shielded from ambient light. Very low leakage can be achieved by using a diode-connected FET as shown. The 2N4117A is specified at 1pA and its metal case shields the junction from light. Sometimes input protection is required on I/V converters of inverting amplifiers (Figure 7b). Although in normal opera- tion, the voltage at the summing junction will be near zero (equal to the offset voltage of the amplifier), large input transients may cause this node to exceed 2V beyond the power supplies. In this case, the summing junction should be protected with diode clamps connected to ground. Even with the low voltage present at the summing junction, common signal diodes may have excessive leakage current. Since the reverse voltage on these diodes is clamped, a diode-connected signal transistor can be used as an inexpen- sive low leakage diode (Figure 7b). FIGURE 7. Input Protection Circuits. – + –V S +V S Optional R S V O D: IN4148 — 25nA Leakage 2N4117A — 1pA Leakage (a) = – + I IN V O D D D (b) D D: 2N3904 = NC Siliconix OPA627 OPA627 FPO When used as a unity-gain buffer, large common-mode input voltage steps produce transient variations in input-stage currents. This causes the rising edge to be slower and falling edges to be faster than nominal slew rates observed in higher-gain circuits. (A) (B) SMALL SIGNAL RESPONSE LARGE SIGNAL RESPONSE FIGURE 8. OPA627 Dynamic Performance, G = +1. – + OPA627 G = 1 |
Similar Part No. - OPA627AUE4 |
|
Similar Description - OPA627AUE4 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |