Texas Instruments THS3001 Rev. A, Inverting Gain +, RF +*R1+*R4, Noninverting Gain +1, R4 R5

Description

Figure 1±4. THS3001 Rev. A EVM Schematic

	J1					VCC	C2
							6.8 μF
±VCC	1	±VCC
	2						+
GND							C3
	3
VCC		VCC		R2	R4		0.1 μF
			J2
		±IN		1 kΩ	1 kΩ
		Inverting	R1			7
					2
			49.9 Ω
						±	R5	J4
Rev. A						U1	6 49.9 Ω
								Out
			J3			THS3001
		+IN			3
						+	C4
		Noninverting
			R3			4	0.1 μF
			49.9 Ω
							C1
							6.8 μF
							+
						±VCC

Even though the THS3001 is a current-feedback amplifier, the gain of the EVM can easily be changed to support a particular application by simply changing the ratio of resistors R1, R4, and R5 (R1, R2, and R4 for Rev. A) as described in the following equations:

Inverting Gain +	*RF +*R1 +*R4				(Rev. A)
	RG		R5	R2
Noninverting Gain +1 )		RF	+1 )	R1	+1 )		R4	(Rev. A)
		RG		R4 )R5		R2 )R1

In addition, some applications, such as those for video, may require the use of 75-Ωcable and 75-ΩEVM input termination and output isolation resistors.

Any of the resistors on the EVM board can be replaced with a resistor of a different value; however, care must be taken because the surface-mount solder pads on the board are somewhat fragile and will not survive many desoldering/soldering operations.

Because of the current feedback architecture, extra care must be taken to ensure that a feedback resistor is always included in the design. In addition, there must never be a capacitor directly in the feedback path between the amplifier output and the noninverting input. Disregarding this guideline will likely result in a part that oscillates.

1-4 General Information