Features

lm6172 is a dual high -speed voltage feedback (unless otherwise explained, it is typical)

amplifier. The unit gain is stable and the performance is excellent

Easy -to -use voltage feedback topology and communication performance. The unit gain 100MHz

High conversion rate 3000V/μs bandwidth, 3000V/μS conversion rate and 50mA output

Wide unit gain bandwidth, 100MHz per channel, LM6172 provides the performance of high dual amplifiers; It only consumes

low power current 2.3mA/channel 2.3mA/channel.

High -output current 50mA/channel

LM6172 works under the supply of ± 15V

suitable for ± 15V and ± 5V operating systems that require large voltage fluctuations, such as ADSL, scanning, scanning Instrument and ultrasonic equipment. It also applies to the low -voltage power supply of ± 5V

Portable video system and other applications.

Scanner I-V converter

ADSL/HDSL driver LM6172 uses TI's advanced VIP III (vertical integrated PNP) complementary bipolar multimedia broadcast system process. See LM6171 data table

Video amplifier with the same function.

NTSC, PAL, and SECAM system

ADC/DAC buffer

Pulse amplifier and peak detector

Absolute maximum rated value (1) (2)

(1) Absolute maximum rated value indicates the limit that the device may be damaged. Run the rated value indicates the expected function of the device, but the specific performance cannot be guaranteed. Guarantee specifications and test conditions, see electrical characteristics.

(2) If you need military/aviation special equipment, please contact the Texas Instrument Sales Office/dealer to obtain availability and specifications.

(3) Human model, 1.5kΩ connects 100pf. Machine model, 200Ω with 100pf series.

(4) Continuous short -circuit operations can lead to more than a maximum allowed temperature of 150 ° C.

(5) The maximum power consumption is the functions of TJ (MAX), θJa, and TA. The maximum allowable power consumption temperature in any environment is pd (TJ (MAX) – TA)/θJa. All numbers are suitable for packaging directly welded to the PC board.

± 5V DC special characteristics

Unless there are other regulations, it is guaranteed to ensure that TJ 25 ° C, V+ +15V, V-15V, VCM 0V and RL 1kΩ limit. Black body limit is suitable for extreme temperature

(1) Typical value represents the most likely parameter method.

(2) ensure all the limit through testing or statistical analysis.

± 5V DC special characteristics

Unless there are other regulations, it is guaranteed to guarantee all limits of TJ 25 ° C, V+ +15V, V-15V, VCM 0V and RL 1kΩ value. The limit of the black body is suitable for extreme temperature (continued)

(3) The large signal voltage gain is the total output distribution to generate the input signal required to generate a swing. For vs ± 5V, vout ± 5V. For vs ± 5V, vout ± 1v.

(4) The opening output current of the opening is 100Ω load resistance removed by the output of the resistor.

± 5V AC electrical characteristics

Unless there are other regulations, TJ 25 ° C, V+ +15V, V-15V, VCM 0V, RL 1kΩ

(1) Typical values represent the most likely parameter method.

(2) Differential gain and phase are measured at 3.58MHz, measured by av +2, vin 1VPP measurement, and the input and output terminals are 75Ω.

(3) Use AV +2, VIN 1VPP, and RL 100Ω to measure harmonics.

± 5V DC special characteristics

Unless there are other regulations, it is guaranteed to ensure that TJ 25 ° C, V+ +5V, V-5V, VCM 0V and RL 1 KΩ Limited value. Black body limit is used at extreme temperature

(1) The typical value indicates the most likely parameter method.

(2) ensure all the limit through testing or statistical analysis.

(3) Large signal voltage gain is the total output amplitude divided by input signal to generate the required. For vs ? 5V, VOUT ? 5V. For vs ? 5V, VOUT ? 1V.

(4) The opening output current of the opening is 100Ω load resistance removed by the output of the resistor.

LM6172 Performance Discussion

LM6172 is a double high -speed, low work Consumption, voltage feedback amplifier. It is a unified obtaining stability and providing excellence. Each channel is only 2.3mA power supply. The combination bandwidth of 100MHz unit gain, 3000V/μS conversion rate, 50mA/The channel output current and other attractive features enable LM6172 in various applications. The static power of the LM6172 is 138MW, and the working voltage is ± 15V power supply and 46MW. Under the ± 5V power supply. LM6172 circuit operates the AB class input level in LM6172 is completely symmetrical and has a feedback amplifier similar to a circular features similar to a current. In the figure, Q1 to Q4 constitutes the equivalent value of the current feedback input buffer, that is, the equivalent effect on the feedback resistor, and the A -class buffer inverse input. The three buffer transfers to isolate the gain level from the load to provide low output impedance.

LM6172 Return Return Promotion feature

The turnover rate of LM6172 determines the impedance node capacitor by the internal high voltage charging and discharge current. This current is the differential input voltage removal with a total degradation resistance. Therefore, the conversion rate is proportional to the input voltage level, at a low -gain configuration. When a very large signal pulse is applied to the input end of the amplifier, there will be some excess or overwhelming. By placing an external series resistor (such as 1kΩ) at the input terminal of LM6172, the conversion rate can be reduced to help reduce overwhelming and reduce the settlement time. Shortening the settlement time LM6172 has a very fast rotation rate, leading to a super -reconciliation. Reduce precipitation time LM6172, a 1kΩ resistor can connect with the input signal to reduce the conversion rate. Feedback capacitors can also be used to reduce overburning and overwhelming. This feedback capacitor is used as zero to increase the stability of the amplifier circuit. It is recommended to initially evaluate the use of 2PF feedback capacitors. When the LM6172 configuration is configured as a buffer, a 1kΩ feedback resistance must be added to the feedback cover

Drive the capacitance load

The amplifier that drives the capacitance load can oscillate or ring the bell at the output end. When eliminating oscillation or reducing bells, the isolation resistance can be placed according to the figure. Isolation resistance and load capacitors form a polar point to increase stability by adding more phase margin to the entire system. The required performance depends on the value of the isolation resistance; the larger the isolation resistance, the more pulse the stress becomes slow. For LM6172, it is recommended to initially use the 50Ω isolation resistance evaluation.

The layout is considered Print circuit board and high -speed computing amplifier

in the design of the design There are many things that need to be considered when the PC board used for high -speed computing amplifiers. If you are not careful, in high -speed circuits, it is easy to have excessive oscillation, oscillation and other performance reduction. Generally speaking, the signal trajectory should be short and wide to provide a path of low inductance and low impedance. Any unused board space needs to be grounded to reduce the picker of the strange signals. Key components should also be grounded at the public point to eliminate voltage drops. The socket will add a capacitor to the circuit board and may affect the frequency performance. It is best to weld the amplifier directly on the PC board without using any socket.

Use probe

The active (FET) probe is an ideal choice for high -frequency measurement, because they have broad bandwidth, high input impedance and low input capacitors. However, the probe ground wire provides a long -connected loop to produce measurement errors. Instead, the probe can be directly grounded by removing the grounding line, the probe cover and the use range probe can be directly grounded.

Component selection and feedback resistance

In high -speed applications, it is important to keep all component leads short, because the wires have inductive frequencies at high speed. For separate components, choose carbon composite resistors and cloud -mother capacitors. Surface installation components are more likely to produce minimal inductor effects. The high value of the feedback resistance may be coupled with parasitic capacitors and cause adverse effects, such as bells or oscillations in high -speed amplifiers. For LM6172, the feedback resistance of less than 1kΩ gives the best.

Input capacitance compensation

The combination of the input capacitor and gain setting resistance of the amplifier increased by a pole, which can cause peak or oscillation. To solve this problem, a value is CF GT; (RG × CIN)/RF (1) that can be used to cancel that rod. For LM6172, it is recommended to use 2PF feedback capacitors. The diagram shows the compensation circuit.

Power sources

Winging power supply is necessary to maintain low power impedance cross -frequency. The two should be placed by 0.01 μF ceramic capacitors to bypass the positive and negative power supply directly to the power pipe foot and 2.2 μF 钽 capacitors near the power pipe foot.

Termination

In high -frequency applications, if the signal is not terminated, reflection will occur. Figure 48 shows the correct termination signal, and FIG. 49 shows the incorrect termination signal.

In order to reduce the reflection, the coaxial cable with the signal source with the signal source should be used. The other end of the cable should be connected to the end of the same value or resistor. For commonly used cables, the characteristic impedance of RG59 is 75Ω, and the characteristic impedance of RG58 is 50Ω.

Power consumption

The maximum power of the device allows dissipated power as: pd (tj (max) -ta)/θja

PD is the power consumption in the device [ 123]

TJ (MAX) is the maximum knot temperature

TA is the ambient temperature

θja is the thermal resistance of specific packaging

For example, for SOIC-8 packaging The maximum power consumption temperature in the LM6172, 25 ° C environment is 780MW. Thermal resistance θJa depends on parameters such as mold size, packaging size and packaging materials. The smaller the size and packaging of this mold, the higher the θja. 8 -needle DIP packaging is lowThe heat resistance (95 ° C/W) is higher than 8 stitches SO (160 ° C/W).Therefore, in order to obtain higher dispersion capabilities, use 8-needle dipping packaging.The total power consumption of the device can be calculated as: PD PQ+PL

(2)

PQ is a static power dispersed in the device without load connections at the output end.Whether the profit and loss of energy dissipate in a device with loads connected to the output end; it is not the power consumed by the load.In addition,

PQ Power supply current X's total power supply voltage

PL output current X (the voltage difference between the power supply voltage and output voltage of the same power supply) for example, VS ± 5VThe total power consumed by the LM6172 of the two channels of LM6172 is 10V to 1kΩ.+100MW 238 MW