Philips Semiconductors | Application note |
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Using the NE/SA5234 amplifier | AN1651 |
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Author: L. Hadley | 2.5MHz is retained. Slew rate is 0.8V/μs and each op amp will |
| settle to a 1% of nominal level within 1.4μs. |
I. SUMMARY
The NE/SA5234 is a unique
Most notable are the input and output dynamic range characteristics of the individual op amps. The
The frequency related characteristics are also above average for low voltage devices in this class. Internal unity gain compensation makes the NE5234 very resistant to any tendency to oscillate in low
II. DETAILED DESCRIPTION
Input Stage
The input differential amplifier consists of a compound transistor structure of parallel NPN and PNP transistors which account for the unique
In the
VCC
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| R10 |
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| R11 |
| IP |
| VB2 |
| IB1 |
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| Q10 | Q12 |
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| VB1 | + |
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| Q2 | Q2 |
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(+) | Q3 | Q4 | ± |
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| Q5 | VBIAS |
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| SWITCH | |
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| Q8 | Q9 |
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| IN |
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IN(±) |
| R8 | R9 |
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| Q7 | Q6 |
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SL00630
Figure 1. NE5234 Input Stage
Linear operation between the two modes is governed by a current steering circuit consisting of Q5,6 and 7 in conjunction with voltage reference VB1. Operation in the
Operation in the
collector junction to become forward biased (base current flow directly to the collector circuit) reversing the collector current flow direction. In a conventional op amp, this would have the adverse effect of reversing the output signal polarity as the operating region is traversed by the input signal. (see Figure 2)
To prevent this from occurring, large geometry
1991 Oct | 2 |