KH207 查看數據表（PDF） - Cadeka Microcircuits LLC.

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KH207

Low Distortion Wideband Op Amp

Cadeka Microcircuits LLC. 

KH207

+Vcc

Rc

12Ω

Q1

(MJE170)

Q3

(2N3906)

to pin 12

to pin 10

0.01ΩF

Rx

14.3kΩ

0.01ΩF

Q2

(MJE180)

Rc

12Ω

Q4

(2N3904)

-Vcc

DATA SHEET

Noise Analysis

Approximate noise figure can be determined for the

KH207 using the Equivalent Input Noise plot on page 3

and the equations shown below.

kT = 4.00 x 10-21 Joules at 290°K

Vn is spot noise voltage (V/√Hz)

in is non-inverting spot noise current (A/√Hz)

ii is inverting spot noise current (A/√Hz)

Rs

+

Ro

Rn

KH207

-

Rf

Rg

Figure 4: Active Current Limit Circuit (50mA)

Controlling Bandwidth and Passband Response

In most applications, a feedback resistoKr value of 2kΩ

will provide optimum performance; nonetheless, some

applications may require a resistor of some other value.

The response versus Rf plot on the previous page shows

how decreasing Rf will increase bandwidth (and frequency

response peaking, which may lead to instability).

Conversely, large values of feedback resistance tend to

roll off the response.

The best settling time performance requires the use of an

external feedback resistor (use of the internal resistor

results in a 0.1% to 0.2% settling tail). The settling

performance may be improved slightly by adding a

capacitance of 0.4pF in parallel with the feedback

resistor (settling time specifications reflect performance

with an external feedback resistor but with no external

capacitance).

Thermal Model

Tcase

100°C/W

Tj(pnp)

Ppnp

100°C/W

Tj(npn)

Pnpn

17.5°C/W

Tj(circuit)

Pcircuit

θca

+

-

Tambient

Pcircuit = [(+VCC) – (-VCC)]2 / 1.77kΩ

Pxxx = [(±VCC) – Vout – (Icol) (Rcol + 6)] (Icol)

(% duty cycle)

(For positive Vo and VCC, this is the power in the npn output stage.)

(For negative Vo and VCC, this is the power in the pnp output stage.)

θca = 65°C/W in still air without a heatsink.

35°C/W in still air without a Thermalloy 2268.

15°C/W in 300ft/min air with a Thermalloy 2268

(Thermalloy 2240 works equally well.)

Icol = Vout/Rload or 3mA, whichever is greater.

(Include feedback R in Rload.)

Rcol is a resistor (33Ω recommended) between the xxx collector and ±VCC.

Tj (pnp) = Ppnp (100 + θca) + (Pcir + Pnpn)θca + Ta, similar for Tj (npn).

Tj (cir) = Pcir (17.5 + θca) + (Ppnp + Pnpn)θca + Ta.

F

=

10 log









1+

R

R

s

n

+

Rs

4 kT



⋅





i

2

n

+

V

2

n

R

2

p

+

R

2

f

i

2

i

R

2

p

A

2

v













where R p

= Rs Rn

Rs +Rn

;

Av

= Rf

Rg

+1

Figure 5: Noise Figure Diagram and Equations

(Noise Figure is for the Network Inside this Box.)

Driving Cables and Capacitive Loads

When driving cables, double termination is used to

prevent reflections. For capacitive load applications, a

small series resistor at the output of the KH207 will

improve stability and settling performance.

Transmission Line Matching

One method for matching the characteristic impedance

(Zo) of a transmission line or cable is to place the

appropriate resistor at the input or output of the amplifier.

Figure 6 shows typical inverting and non-inverting circuit

configurations for matching transmission lines.

R1

Z0

R3

C6

V1

+

-

+

R2

KH207

-

R6

Z0

Vo

R7

R4

Z0

Rg

Rf

V2

+

-

R5

Figure 6: Transmission Line Matching

Non-inverting gain applications:

s Connect Rg directly to ground.

s Make R1, R2, R6, and R7 equal to Zo.

s Use R3 to isolate the amplifier from reactive

loading caused by the transmission line,

or by parasitics.

REV. 1A January 2004

5

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