DO-204 is a family of semiconductor packages defined by JEDEC

JEDEC

The JEDEC Solid State Technology Association, formerly known as the Joint Electron Devices Engineering Council , is an independent semiconductor engineering trade organization and standardization body...

. This family comprises lead-mounted axial devices with round leads. Several common packages such as DO-41 are archived in DO-204 as variants.

Generally a diode will have a line painted near the cathode

Cathode

A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...

 end.

Variants included in DO-204

Variant	Other standards		Dimensions (mm)
			A			B			C			D			E
			min	max		min	max		min	max		min	max		min	max
AA	DO-7		25.40	38.10		5.85	7.65		0.46	0.55		2.16	2.71		—	1.27
AB	DO-14		25.40	38.10		5.85	7.62		0.46	0.55		2.75	3.55		—	1.27
AC	DO-15		25.40	38.10		5.85	7.62		0.69	0.88		2.65	3.55		—	1.27
AD	DO-16		11.43	19.05		1.27	2.54		0.23	0.33		—	1.27		—	1.27
AE	DO-26		35.56	38.10		8.75	10.41		0.69	0.99		5.59	6.60		—	2.03
AF	DO-29		25.40	38.10		8.00	9.14		0.74	0.83		3.05	3.81		—	1.27
AG	DO-34		25.40	38.10		2.16	3.04		0.46	0.55		1.27	1.90		—	1.27
AH	DO-35		25.40	38.10		3.05	5.08		0.46	0.55		1.53	2.28		—	1.27
AJ	—		11.43	13.97		5.85	7.62		0.49	0.53		2.16	2.66		—	1.27
AK	—		11.43	13.97		3.81	4.45		0.36	0.40		1.66	1.90		—	1.27
AL	DO-41		25.40	—		4.07	5.20		0.72	0.86		2.04	2.71		—	1.27
AM	—		17.53	38.10		3.18	5.20		0.64	0.91		1.27	2.79		—	1.27
AN	—		25.40	—		5.08	5.84		0.71	0.86		2.54	3.05		—	1.27
AP	—		25.40	38.10		3.18	4.57		0.74	0.89		2.54	3.81		—	1.27
AR	—		27.95	38.10		9.27	9.52		1.22	1.32		6.10	6.35		—	2.54

DO-35

The DO-35 is a semiconductor package

Semiconductor package

A semiconductor package is a metal, plastic, glass, or ceramic casing containing one or more semiconductor electronic components. Individual discrete components are typically etched in silicon wafer before being cut and assembled in a package...

 type. It is often used to package small signal, low power diodes

Diode

In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...

 such as 1N4148

1N4148

The 1N4148 is a standard silicon switching diode. Its name follows the JEDEC nomenclature. The 1N4148 has a DO-35 glass package and is very useful at high frequencies with a reverse recovery time of no more than 4ns. It was second sourced by many manufacturers; Texas Instruments listed their...

 (a 100V, 300mA silicon diode.)

DO-41

The DO-41 is a common package used to encapsulate rectifier

Rectifier

A rectifier is an electrical device that converts alternating current , which periodically reverses direction, to direct current , which flows in only one direction. The process is known as rectification...

 diodes. The name is derived from the JEDEC

JEDEC

The JEDEC Solid State Technology Association, formerly known as the Joint Electron Devices Engineering Council , is an independent semiconductor engineering trade organization and standardization body...

 descriptor "Diode Outline, Case Style 41". DO-41 diodes are larger than signal diode packages such as DO-35, which are not required to handle large currents.

The most common diode using this packaging is the 1N400X series of rectification diodes.